WHAT!?! You comparing the A4 with the 3-series and C-Class? Now it's my turn to be dissapointed in you. (hehehe) IMHO the current 3-series is downright fugly. The new C-class is very handsome and the A4 is the brute of the lot. I'd go for brute anytime and gotta love that S4 with the 19" rims and bodykit. Going over potholes? No problem, you won't feel a thing. Cornering? Magneto-thingy-whatchamacallit stiffens up the suspensions and corner like a god and oh... helloooo Quattro!
I think the IS is not too shabby in the looks department but if it was the same money as a A4, I wouldn't think twice about getting that A4.
Oh come on man, the RS and the S range of those Audis are awesome handling and performance machines. The RS4 was on par with the M3 in tests but most reviewers are enthusiasts and any enthusiast will always say RWD will always be more fun compared to 4WD.
And I think the word you're looking for is "Soul".
Not a lot of cars have that kind of feel.