SECOND PLACE - AUDI S6
The S6--like its big brother, the S8--benefits from a charismatic engine. Rated at 435 hp, the V-10 with Italian DNA features direct fuel injection, four overhead camshafts, and an intake plenum with two unequal-volume lungs. Drop the hammer, and the S6 catapults itself into action, generating tidal waves of noise that sound so physical they might result in the car's flight path being lined with leafless trees and featherless birds. The gearbox programs are mapped much more closely together than those in the Benz, but manual mode further speeds up the gearchanges, and in the sport setting, the engine revs greedily to its 7000-rpm redline. Thanks to Quattro, traction is never an issue, and grip is magnetic. Torque is split 40/60 percent front to rear, but this rear-wheel bias is recalculated at the first hint of wheel spin. The Audi has the most riveting brakes, and its steering is reassuringly competent in managing the sometimes antagonistic propulsion and direction-changing duties.
We expected the S6 to be notably slower and less involving, with more androgynous handling qualities and less feedback overall. But we were wrong. Despite the near total absence of drama, its set of reflexes is complete. Quattro is a bonus not only in winter or when it rains: it also ties the car down well through dips and brows, makes carving the twisties much more relaxed, and always--always--puts the power down. Instead of bothering you with weight distribution or traction-control issues, the S6 simply goes where you point it. No, power oversteer is not easily induced, but when you whip all three cars through a wet corner, there is one clear winner. And at an estimated $75,000, the Audi is the most affordable supersedan.
FIRST PLACE - MERCEDES-BENZ E63 AMG
What makes the E63 so special is the blend of its abilities. For a start, it's a particularly emotional machine-mean-looking, acoustically overwhelming, and very fast, yet it can be either velvety smooth or bondage brutal, whichever you wish. True, the stability-control warning light may flash in the wet at 125 mph, but you won't feel more than a tug or a kick, and then it's full urge again all the way to the 7200-rpm redline. Unlike the supercharged E55, which was so pumped up with hormones it could hardly accelerate in a straight line, the follow-up model is a lot more relaxed, more sure-footed, and quite a bit quicker. By a wafer-thin margin, the Benz has the most compelling engine. It wins the torque trophy and the acceleration medal, it sounds awesome, it's mated to a transmission that confines itself to only three shift programs, and its relentless push extends into the triple-digit speed zone. What this car needs to move even closer to perfection are brakes with extra staying power and steering that can do more than change direction.
Even under pressure, the nose of the E63 finds it easy to stay close to the apex. As a result, the driver is more inclined to light up the rear tires in crowd-stopping fashion. The trouble is that you can slide the Benz only with stability control off, so there is no intermediate safety net such as M Dynamic Mode in the M5 or traction control off in the S6. Unlike the BMW, which feels a little twitchy as it nears the limit of adhesion, the AMG hugs the tarmac. There is also less lift-off weight transfer, less acceleration squat, and less brake dive, and, despite the subdued body movements, you always know where you are on the speed and g-force map.
At an expected $85,000, the Benz digs deepest into the budget, but it is worth every penny--against the stopwatch and in smiles-per-miles currency. It wins on merit and appeal, even though it surpasses the S6 only by a whisker.
The fact that the M5 has fallen so far so fast tells you three things: That this is an extremely fast-moving business. That even a well-founded status quo can be eroded by clever evolution. And that the big-engine-in-a-mid-size-car game is more competitive than ever.