Nvidia GeForce 6800 GS reference card
Real overclocking potential
Moving on a real game, Far Cry, we see the GS again falling behind the GT, though it's very close, indeed being less than a single frame in most cases. Doom 3 is behind by the same narrow margin while Half Life 2 is up from the GT, though again the difference is minor.
At the sweet spot of 1280 x 1024 with 4x FSAA and 8xAF you'll get around 45 and 55fps depending on the game, which is playable, though you'll probably have to turn it down for online shooters where frame rate is king.