Last year had Lost Planet, Supreme Commander, and Crysis, all of which rape even high-end machines (Lost Planet less so than the other two, but still brutal as hell. It's a slideshow in DX10 1920x1200 on my rig unless I drop settings significantly).
Other than those beastly, brutal supergames, a 9600GT should be more than adequate below 1920x1200, at that res you'll still want the 8800. Either GT or GTS, they're fairly similar. I like the dual-slot cooler on the GTS, personally.