I really just need to quit expecting so much out of my X800. Although I paid $400 for it, its no where near a 6800 GT and I need to quit expecting that kind of performance out of it.
Its quite common for the Pro model X800 to experience these problems in Doom 3, first because Doom 3 was coded to have an advantage on Nvidia hardware and second, because the 12 pipes just can't keep up in this particular game, most likely because of the shadows and the massive fill rate requirements to be able to render shadows with the kind of detail the shadows in Doom 3 have. And this card is just going to keep getting worse because the Pixel Shader 3 era is upon us, and much of the eye candy of future games is going to come from Pixel Shader 3 effects.
This is why everybody I know who bought the X800 Pro has already exchanged it out or sold it and got a 6800 GT.