Beware BMW 5 Series and Mercedes-Benz E-Class: the Audi A6 no longer needs any introduction and is coming for you. Between the basic 252-horsepower engine and the S6's insane 450-horsepower V8, there's a 3.0L V6 that generates 333 horsepower (340 for the Competition version). All versions come with all-wheel drive. Since Audi belongs to Volkswagen, the diesel engine is no longer offered for the A6—not for the moment, anyway.