I chose three DX10 games that really are hard on a system, and all have incredible graphics, Crysis, Call of Juarez, and PT Boats-Knights of the Sea. All three games require strong, stable systems to perform, any of the three will easily crash on a system that is the least unstable.
Everyone into gaming has heard of Crysis, for better or for worse. The graphics are pretty incredible, but you need a strong system to play it with any kind of success. I used the Crysis Benchmark written by Boris "MadBoris" Veriga. The settings I used were: Medium, GPU Benchmark, DX10, no AA, and 1280 x 1024.
On paper, the extra FPS doesn't look like much, but there was really no comparison between the older cards and the 9600GT. Everything looked so much smoother, mainly due to a higher minimum FPS.
Call of Juarez is a DX10 FPS in an "old west" setting. The graphics are the most awesome that I have seen yet, the detail is so totally incredible on everything. This game is best played on a decent video card, though most cards fare a little better on the game itself than on the benchmark. Settings were: Balanced, AA x 2, 1280 x 1024.
Needless to say, there was no comparison between the 9600GT and the older cards, which do much better on the game with no AA. The 9600GT is the first mid-grade card I've seen that performs reasonably well running some AA.
PT Boats - Knights of the Sea is an ocean-based game with some really detailed water graphics. Before this game, I never really thought about how complicated graphics on water could be, such as the flashes from guns on rough water. Setttings were: High, AA x 2, 1280 x 1024.
Again the 9600GT really outperformed the other cards, this time getting twice the FPS as the 8 series cards.