The RS4 was rushed out fast by Audi when they first heard/realized that the new M3 would have a V8. It's a very non-special car compared to the upcoming new M3. Even the quattro transmission on it reduces the actual output of the engine going to the wheels big time, over 17% power loss in transmission, and this for a supposedly "special" model. That's nothing new in regular Audis or VW concern 4WD's, but for the RS4, it's a shame. They're desperately trying to cash in as much as they can now before the new M3 hits the streets, because there is no direct competition from BMW, with the M5/M6 being too big, heavy and expensive and non-comparable.
Mark my words: In the next 10 years or so, Audi will probably build an all RWD car. They've moved the percentage of power to the rear wheels more and more, trying to cope with BMW on the market and trying to make cars that are as fun to drive, but they just can't - unless they do an RWD only car. Remember that Quattro used to be advertised as the perfect 4WD with 50:50 power distribution... Now it's way more RWD oriented already, and keeps getting that way. But their worst problem is their low standard of engine engineering (both turbodiesels and gasoline.) Even the RS4 V8 is basically, well, garbage, when compared to the new M3 power-unit. In it's revs, transmission, etc.
They also tried to copy the M5/M6 with the S6 unsuccessfully by building their own V10 gasoline engine, and in this case, BMW had the goods out on the market first. And they were better to start with. The current S6 is a pathetic M5-wannabe.