the only thing about the 7600 i didnt like is its 128 bit ram... while the 6800gs has 256 bit... i don't know how they compare side to side.. but give me a few minutes and i'll tell you how they stack up to each other...
as for the radeons... i just plain wouldnt suggest them.. because i hear.. supposedly, that most radeons other than the X1XX series have problems and don't support alot of new features