| posts: 6,454 | Location: Oregon
Well I can tell ya from recent personal experience lol.
Two of my comp's listed below, one has a 2400+, one has a 2500+. The 2500+ has a 9550 overclocked to 9600Pro speeds, and the other has a 128mb pure 8500 (not LE, 275/275).
They are virtually identical in DX8 games..ie Battlefield 1942 and 3dmark01. In DX9 though (specifically, Guild Wars) the 9600 is seriously faster...easily double the framerate and 3dmark03 scores. Plus it looks better since it is using the dx9 path.
So there is no reason not to swap for the 9600.