What kind of world do we live in where a 255-350 horsepower luxury sedan isn’t enough? Answer: a most righteous one. Audi engineers pushed aside the A6’s 3.2-liter V6 and 4.2-liter V8, opting to outfit the lineup’s resident brute, the 4,486-lb. S6, with a normally-aspirated V10 that features direct injection. Featuring 5.2-liters of displacement, a 12.5:1 compression ratio and dual overhead cams, this 40-valve aluminum engine boasts 435 horsepower at 6,800 rpm and 398 lb.-ft. of torque at 3,500 rpm (90 percent of the total torque is available between 2,300 and 6,200 rpm).