(FORTUNE Magazine) – Lots of life's variables are in constant flux--gas prices, the value of all those stock options, the heft of Bill Gates' wallet. But one thing that doesn't seem to change is what happens when you hit your middle years: You experience an overwhelming urge to possess a hopelessly impractical automobile.

There are several must-have qualities in the perfect midlife-crisis car. First and most obvious, the vehicle must score high in the looks department. Second, it must, when you fire up the engine, inspire a spike in your pulse rate that would worry your cardiologist. Third, it should immediately gain you rock-star parking wherever you go. Fourth, it should provoke, well, steamy NC-17-and-beyond sorts of feelings.

I am queasily qualified to discuss midlife motors because I recently celebrated my double 20th birthday, as I prefer to call it. And for that day, my husband, who is in the business of building ultra-high-performance cars, delivered to me a 550-horsepower twin-turbo Callaway Speedster, a bottle-glass-green topless two-seater that pumps out nearly 700 ft-lbs of torque. (These cars are no longer available; mine is the last of a 12-car series he produced 14 years ago.) That means wheel spin in every gear at only 3,000 rpm. It has the power to scare the bejesus out of me, just driving to the store. I love it. A male friend saw the car and said, "My God, your husband must really trust you!" I replied that of course he knows I can handle such a powerful car--it's one of the things I do for a living. "No," he shot back, "I mean, every man in the world will be chasing you in that thing."

And therein lies the fifth and final quality of a perfect midlife-crisis car: Thy Friends Shalt Covet. In other words, it must make others feel the heat too. (No kidding: Recently one bystander reacted to my car's mojo so strongly that while I was stopped at a red light he proposed marriage from the sidewalk.)

A spate of options in the sex-on-wheels category litters dealer lots right now. But numero uno is the 2004 Porsche Carrera GT. Unlike other supercars such as the Ferrari Enzo, SLR McLaren, and Lamborghini Murcielago, the Carrera GT is neither a stripped-down racecar nor a pumped-up street car. Rather, the mid-engine two-seater is based on a concept racecar that Porsche built in 1999 for Le Mans. (Lucky for us that the competition budget got cut.) It has since been refined into a fully finished street car.

The Carrera GT is a cocktail of function and form so brilliantly balanced that I found myself needing to take another swat at the throttle, caress the center-console-mounted shift, and admire the body from different angles. (The rear three-quarter view is the most drool-inducing, showing the car's long, muscular back and arching extended headrests that double as a very sexy engine cover.) The Porsche ceramic composite clutch and brakes are lighter and more capable than the systems in other production cars. The carbon-fiber monocoque is the stiffest and lightest Porsche has ever fabricated. The V-10 engine sits low enough to achieve superb balance and stability. Even the paint is special: Its patented formula prevents the weave of the carbon fiber from ever showing through. Such perfection has its price: $440,000. For that kingly sum you will get one of only 1,500 to be built over the next three years.

I wanted to experience such a rare car with a rare companion. So I found a Carrera GT owner whose life has been a series of adventures most of us can only dream about. Otis Chandler, retired publisher of the Los Angeles Times and former chairman of Times-Mirror, bikes hundreds of miles weekly--and he's 76. He has hunted big game worldwide. He has owned and raced some of the greatest cars on the planet; a few times a year his collection, housed at the Vintage Museum of Transportation and Wildlife in Oxnard, Calif., opens to the public (www.chandlerwheels.com). You'll see everything there from rare Duesenbergs to a taxidermied Marco Polo bighorn sheep he got at 19,000 feet in Afghanistan. But you will find only one current-generation supercar: the Carrera GT. "I have never driven anything quite as exciting and manageable as this street-legal car," Chandler says. "It is a milestone."

Amen, brother. I took his silver weapon for a spin along California's coast and through the nearby labyrinthine Malibu canyons. And what a ride it was. The car's 605-hp V-10 drowned out every stray thought in my head as it belted out pure power with an intensity to make a diva blush. I looked down at the huge tachometer dead ahead on the dash; 6,000 rpm in third gear equals 90 mph. Not too shabby, considering there are three more gears to go and an 8,400-rpm redline for each one. The rest of the controls are blissfully sparse: merely climate, windows, and the inevitably unworkable Porsche stereo. As I shifted to fourth, I touched wood for luck--in this case, the matte-finish birch shifter knob, a nod to Porsche racing heritage in an otherwise futuristic, magnesium-filled cockpit.

Up where the roads got wild and other cars grew scarce, I threw the Carrera GT into corners. I stabbed at the brake pedal. I decked the throttle until I ran out of road. And yet, no near-death flashes, no adrenaline-soaked panics. As I exhausted tests of its might, I realized that this magnificent machine is smarter than any driver. Its weight balance means you can't brazenly throw out the rear end, and its electronic controls, from the antilock brakes to the traction control, are set to limits higher than the street driver can easily find. I've never had more fun trying to get a car to misbehave.

Some car writers have nitpicked that the Carrera GT's pedals are too close; that storage is at an all-time minimum (my favorite innovation is a tiny tubular compartment in the door edge that holds a pair of sunglasses); and that the ruler-narrow sun visors are useless. How sad to miss the simple point that this car is the epitome of engineering prowess, from a company known for its engineering prowess.

Don't feel like dropping $444,000 to get your automotive ya-yas out? Thanks to a renaissance of fun little sports cars coming to these shores, the options for those who want to spend a tenth of that are wider than ever. BMW's Mini Cooper S and the Mazdaspeed Miata (a high-performance version of the base car) are great examples. However, the most playful, track-ready, and attention-grabbing is the Lotus Elise. The obvious allure is its shazaaam! styling. Like some extreme cartoon machine, the Elise--which British maker Lotus just brought to the U.S. after years of success in Europe--is a swoopy insect whose shape people either love or hate.

But the greatest thing about the stiff-bodied Elise is that you can throw it around on regular roads and still give yourself a real thrill. It feels and responds like a go-kart--a high-performance experience without life-threatening power. I pushed the little gremlin hard and could feel its limits; a particularly tight downhill corner springs to memory, when the mid-engine car's rear end swung out midturn as I backed off the throttle. And yet the Elise showed good breeding: Its reaction to my roughhousing was to swing wide and then regain its road composure when I counter-steered. Other signs of racecar lineage: Its shifting (it loves to rev around 6,500 rpm) and steering are precise and smooth; its road feel is immediate; and its low-to-the-ground stance puts you at combat level with gravity. Its zero-to-60 time: 4.4 seconds.

I took a British Racing Green Elise to my local Saturday sunrise car show in Newport Beach, Calif., the ground zero of midlife-crisis cars. The same morning someone else showed up in a Carrera GT. It was a tossup as to which car attracted more drooling middle-aged men and teenagers. As I struggled to look graceful climbing over the Elise's wide and low doorsill, one particularly enthusiastic gentleman gushed, "The best way into that little thing is to strip naked and coat yourself with oil." Gee, thanks for the advice.

Just don't buy an Elise looking for Lexus-level finish quality. Aside from the exceedingly dependable 190-hp, 1.8-liter four cylinder and six-speed gearbox from Toyota, it ain't there. The perforated tan-leather interior in my press car was showing signs of wear and tear after only 3,000 miles, and I'll bet the exterior won't be far behind. Then again, the Elise isn't about long-term love; it's a thrillingly down-and-dirty $40,000 fling.

Some guys' fantasy is a souped-up version of whatever was cool when they were young. That means customizing a hot rod--or "pimping your ride," to borrow a phrase from MTV's hit car-makeover show. This avenue is not for the faint of heart. Some car folks snub customized cars as homebuilt Frankensteins that lack the reliability of a real production automobile. Even the best require a commitment to the toolbox and auto-parts store. But hot rods can also be some of the most extreme lookers on the road--and deliver some pretty lofty performance numbers too.

Consider my all-time favorite hot rod: the Foose Deuce 0032, based on a 1932 Ford. It was created by Chip Foose, a 40-year-old Southern California native who hosts the TLC car-makeover shows Overhaulin' and Rides. There is only one Deuce 0032, and it resides at the Petersen Automotive Museum in Los Angeles. After some begging, the museum let Foose and me take it out for a spin. While we were moving it from its display stand, I overheard a fan refer to the car--which sits four inches off the ground, is endowed with rakish fenders, and is as black as a new-moon night--as the boss of hot rods. I find that description a gross understatement; it's chairman and CEO.

Once outside, I dropped down into the driver's seat --swathed in supple Italian leather the color of a baseball glove and the texture of kid--and immediately vanished from sight. The car's roof was low enough to shield my eyes like a fedora and the top of the door was as high as my chin. The final touch was the unadjustable seat, which threw me into a low-visibility semi-recline--the perfect pose for such a poseur car. One super-slim shifter knob, three simple dials, and that's it. No door handles, no climate-control knobs, not even an ignition in view. Polished aluminum and leather pedals and steering wheel were my only controls; this was minimalism taken to the max.

I quizzed Foose about the car's 330-hp Corvette engine and its hand-built suspension parts. But once we took off, I realized that the point of this car isn't about the driving feel. I hauled its fine tail down Wilshire Boulevard, the crowds oohing and the LT4 engine rumbling like a pent-up beast between the curvaceous fenders. Precise? No. Full of high-tech engineering? No. The baddest ride around? Yep.

Foose explained that he had designed the car for himself; its quirks, like the seating position, reflect the way he wanted every detail. He'll do that for you too--for $200,000 on up. Just hope for a long midlife moment: There's a four-year wait for his handiwork.

2004 PORSCHE CARRERA GT

Type: Two-seat mid-engine supercar Price: $440,000 Engine: 605-hp V-10 based on a Porsche racing prototype Perks: Profound abilities on the road; unspeakable gorgeousness Owner attitude: I tolerate only the best of the best. More information: Porsche.com

2005 LOTUS ELISE

Type: Two-seat mid-engine sports car Price: From $40,000 Engine: 190-hp 1.8-liter four-cylinder from Toyota Perks: Extreme styling, extreme performance, extreme fun Owner attitude: Move over, Michael Schumacher! More information: Lotuscars.com

FOOSE DEUCE 0032

Type: Two-seat custom-built hot rod based on a 1932 Ford Price: From $200,000 Engine: 330-hp Corvette LT4 V8 Perks: Mind-blowing details; sexiest-car-alive looks Owner attitude: You can't touch this. More information: Chipfoose.com