2007 BMW M6

Probably the engineers at BMW's power-mad M division are eating too much sugar. The team's four-door atom bomb, the new M5 sedan, hasn't even reached our shores yet, and already those hyperactive Bavarians are giddily one-upping themselves by giving us a taste of the M5's more extreme sibling, the 2007 M6 two-door coupe.

More extreme? Than the M5? Which, after all, is a luxury automobile packing a Formula 1-inspired, 500-horsepower V-10 engine that revs like a dentist's drill; a seven-speed, paddle-shift, sequential manual gearbox that Mark Webber might think got stolen from his BMW Williams; and an aluminum suspension so sophisticated you could drive over a newspaper and practically read it. More extreme than that?

Yes. Performance-wise, the M6 is all the M5 is and more. And less, too, in a few key areas where less is in fact more.

The powertrains in the two Ms are identical: that astounding V-10 coupled to the shift-without-a-clutch-pedal seven-speed SMG. Output and gear ratios are the same, too. The M6 edges ahead, then, not with extra muscle but with reduced mass. Up top is a roof made of carbon-fiber-reinforced plastic (CFP), a material BMW first employed on the noggin of the limited-edition M3 CSL. Compared with the conventional steel roof on the 645Ci, the M6's carbon top is 55 percent lighter. Perhaps more important, it also lowers the car's center of gravity by nearly half an inch.

The Jenny Craig treatment doesn't end there. Specially developed, 19-inch forged-aluminum wheels, with spokes as thin as the plot of a Steven Seagal movie, save nearly four pounds per corner over comparable rims, BMW says. The M6 also wears side panels and a rear deck made of lightweight fiberglass-reinforced plastic. And in a move sure to keep M6 owners awake at night with parallel-parking catastrophes dancing in their heads, the bumpers are made of the same exotic CFP as the roof, reducing weight over conventional designs, BMW claims, by 20 percent up front and 40 percent in back--but probably also nudging repair costs up into "we're gonna need a deposit first, sir" territory.