Lost Planet: Extreme Condition
Here's another DX10 game. We ran this game in DirectX 10 mode at 1920x1200 with all of its quality options maxed out, plus 4X AA and 16X anisotropic filtering. We used the game's built-in performance test, which tests two very different levels in the game, a snowy outdoor setting and a cave teeming with flying doodads.

Here's another case where the 8800 GTS 320MB stumbles, while the 8800 GT does not. Although the Radeon HD 2900 XT lists for $399, it looks like an also-ran in most of our tests.