Even at this low resolution all the cards on test struggle with this game. While the HD 2600 XT and 8600 GT are understandably low the fact the 8800 GTX can't break through the 30fps mark really shows how demanding this test is.
Moving to what should be the resolution of choice for midrange cards like the HD 2600 XT and 8600 GT, the situation is even worse. Without AA, the 8800 GTX is just about playable but once AA is enabled all the cards fall into unplayable levels.
Finally, playing at a resolution that should be the perfect match for the 8800 GTX, all the cards are unplayable.
As may be expected considering the supposed advantages offered to ATIs cards the HD 2900 XT and HD 2600 XT offer equal or better performance than the equivalent nVidia parts. However, considering the resolutions you're limited to, none of the cards on test offer satisfactory performance.