B7 RS4 is pretty underwhelming.
Most dyno at around 370ish, nowhere near the claimed 425ish.
I've kept up (just, but nevertheless) with an RS4 , in a diesel , tells you all you need to.
S4 B8 is a very capable car, but boring and feels planted. you're limited with upgrades as well, no uprated bush kits available (well, a few, but very expensive and full metal).
Lexus IS-F would be my fave, they look mean and are different, if not then I'd go for a 5 door M3 e90 in white or blue.