Jedi Knight 2 is a bit of an odd case. Starting off with the non-AA/AF numbers, we can see that the X850 competes directly with the 7800 GTX, though the 7800 manages to take the lead at the very last resolution. The 7800 GT maintains a steady third place. Once we enable AA/AF, the X850 drops like a rock (I'm aware of the laws of gravity, it's just a phrase), and ends up competing with the 6800 Ultra for last place at 1600x1200. The 7800 GT maintains a healthy level of performance throughout.
Halo
In Halo, we can see the 7800 GTX leading, which was expected as this card's performance in the shader-heavy Halo was stellar. Following closely, however, is the 7800 GT. With its average ~10 FPS lag behind the 7800 GTX, I can't quite say that the 7800 GT is only an inkling away from matching the GTX, but it is definitely making its big brother sweat under the collar. Our X850, which manages to stay at a decent pace behind the GT drops behind when AA/AF are enabled, though it still manages to stay ahead of the 6800 Ultra which is (ding ding ding!) last again.