The 2013 S6 is the first year of the Turbo V8 4.0, a much better car in my opinion for the enthusiast than the V10. As we all know much easier to bump in power because it's a Turbo as well as better handling since it is lighter and better balanced with the smaller engine up front. And as Stephen mentioned, the V10's have been high maintenance cars. The V8 doesn't sound as good as the V10 but it is much less thirsty and the Torque curve is much better. The S-tronic is light years ahead of the 5HP24 in efficency but they started to show that they have problems too. An S-tronic tranny is a 50%+ premium over the 5HP24 though, that is in replacement costs.