i would suggest downloading the omega drivers.
They are fine tuned and give good performane. However if you are not happy still, the omegadrivers come with radlinker, a neat overclocking utility. If you want to overclock, just move the speeds up by small increments at a time, and test in between, until it becomes unstable. Once you are happy, run the graphics on something pretty full on (3DMark03 or something) for about half an hour - an hour, and then shut your comp down. Take your case off immediately, and carefully touch the back of your graphics card (directly behind the fan/heatsink and also on the little mem chips). If they are too hot too touch, your card will die soon unless you put a new fan on it, or clock it back a bit.