DON'T try to take this card that high. I have the MSI 8831 GF2 Pro, and the highest i could get the mem stable was 450, it's 5ns DDR...
Those gainwards more than likely have like 4.5 or 4ns ram, which will get the mem clock up to 500+, but ramsinks on the MSI would be next best thing to worthless if you don't have great airflow in yr case. I just dropped $169 on a GF4 Ti4200 (eVGA with VIVO) from
newegg and i'm loving it so far. You wouldn't believe the framerate differences, LOL...