Half Life 2: Aftermath uses 24 bit precision HDR, which can be used by any DirectX 9 compatible video card. All of these benchmarks were run with 4xAA, 8xAF, and HDR enabled.
It's a very close race, but for the first time the X850 XT is a bit humbled compared to the other contestants. The X1800 GTO and 7600 GT are close, but the 7600 GT keeps ahead by a few frames per second. The odd thing is that the Half Life engine used to be a stronghold for Radeon architecture; it's odd to see the 7600 GT with its 128 bit memory interface best the competition here. I'd guess that the GeForce architecture likes the way the HL2 engine implements HDR.
Still, all cards are very playable at 1280x1024 with 4xAA enabled, and on the edge of playable at 1600x1200 with 4xAA enabled. These are very high resolutions for midrange cards to run with anti-aliasing, and they do a great job.
Let's see if the GeForce camp maintains supremacy in the OpenGL arena, with Quake 4.