2003 Audi RS 6 and 2003 Mercedes-Benz E55 AMG

According to the "Hollywood Handbook for Automotive Authenticity & Flames," a fast car should look as follows: roofline lower than prime interest rate, chrome-plated engine parts protruding from hood, rear wing capable of lifting C-130 cargo plane, and--if needed to enhance machismo rating of unusually diminutive male lead--full-length "Starsky" racing stripe.

By those standards, the two discreetly attired sedans pictured here, with their upright four-door profiles, roomy cabins, and distinct lack of peel-'n'-stick "You and What Army?" graphics, should be about as exciting as a midnight rerun on C-SPAN.

Except that the slower of these two cars does 0-60 mph in 4.3 seconds.

You read that right. Each of these seemingly stoic German sedans will transport four adults (five in a pinch) and their luggage as comfortably as a Gulfstream

jet. Yet each is also capable of sending a normally proud Porsche 911 pilot straight to a therapist.

If you like to work up a sweat at the wheel, better shop elsewhere. Here you'll find luxurious, leather-lined cockpits, no-fuss (yet sophisticated) automatic transmissions, and steam-locomotive torque ratings. Annoying little Boxster S in the next lane? Just mash the throttle pedal and humiliate. Quite simply, there isn't a more effortless, exhilarating acceleration experience to be had without needing an ejection seat. Indeed, with the BMW M5 in hibernation until at least the '05 model year (MT, August) and the new Jaguar R models ponying up "only" 390 horsepower, the new Audi RS 6 and the Mercedes-Benz E55 AMG stand alone as the planet's fastest, most thrilling production four-doors.

The question is: Which one of them stands on top?