I dunno if you saw the thread I had going on about my ATI/Linux issue, but I think the ATI Linux drivers from the ATI site should work. I don't know if you'll get any better 3d performance than I did, but the desktop look and available resolutions certainly improved when I installed them.
If it's the same driver as I installed, make sure you run /usr/X11R6/bin/fglrxconfig and reboot.