Moving to an RS4 is moving backwards IMO. In fact your post is the first time I've ever read/heard of anyone with a 6 considering a 4 instead. The RS6 is easily able to extract more power from the engine with just a tune and has more room to drive family and friends around in. It will also always be more attractive than the new RS7. The only thing I plan on swapping any of my rides out with a C5 Avant which I will be able to do in 4 more years.