Serious Sam2 was one of my favourite games when it came out and was a great game to test opengl performance which incidentally has never been a strongpoint for ATI. This game runs well on most of the hardware above apart from the 9600XT and X300 at the very highest settings. The X600XT which is really ATIs "new version" of the 9600 gives almost 10 frames per second extra over its older counterpart at 1600x1200 with 4aa and 16 aniso, the way you want to play games if your monitor can support it.