stress testing for video card?

Hi, I just got an 8800gt 512 and it's awesome compared to the 7600gt I was using before, but it's still lacking sometimes, especially when running crysis on very high, so I was going to overclock it to get a little more oomph out of it. It's stock speed is 625mHz, so I was thinking that an extra 75mHz shouldn't be too hard. Anyways, what program should I use to test for stability after overclocking with rivatuner? I heard that 3dmark was good, but I don't really trust my own eyes to catch all the artifacts

I know that the 8800gt can't run crysis magnificently on full, but that's not the point. I'm just trying to squeeze out a couple more fps, and would like someone to recommend a good stability testing program.

out of interest, how do you do that???

you could just try 3 hours of gaming keeping rivatuner going on hardware monitor in the background so you can keep an eye on temperature. With a gt you might want to tweak the fan settings a bit higher in 3d mode as the stock cooler is a bit pants.

thanks for the suggestions, so far I have been testing with 3dmark06 and ati tool, and they work very well. I've gotten my 8800gt to 702/1704/1902 without a any problems at all. With a stock cooler fan at 80%, is it worth my time to keep trying to go further? temps are 50 idle and mid 60s on load, btw