When I went from air to water, i got nearly a 300mhz gain in my overclock. You should expect to see similar results. As for your 3DMark score, make sure that you've got the latest nForce2 drivers, and all of the settings turned down in the display properties. You should get in the mid to high 8000 range where you're at. Your video card is the main bottleneck, though, so even higher processor overclocking won't do much.