Under the hood of the 2007 Audi S6 is a 5.2-liter, 40-valve V10 engine cranking out 420 horsepower at 6,800 rpm and 397 lb.-ft. of torque at 3,000 rpm, with 368 lb.-ft. of twist being available at only 2,000 rpm. Those generous ratings allow the 4,210-lb. S6 to reach 60 mph in just 5.1 seconds, and push this quattro-equipped sedan to an electronically-limited top speed of 155 mph. A six-speed Tiptronic automatic transmission with a Sport mode and shift paddles on the steering wheel is standard.