(For me, all these scores are without an overclock.)
The 6800 should be good. The PCI-E version is a slightly lower clocked version, which I have. I can play at 1280x1024 ALL HIGH in Battlefield 2 with 60 FPS or so. That means the AGP version should be a little faster. 4xAA slows down BF2 to ~35 FPS. With HL2 I get even more than 60 FPS, easily, without AA. With 4xAA, it's about 60 FPS. If you get lucky, you can unlock the 6800NU AGP to get 16 pixel pipelines and 6 vertex pipelines. That along with overclocking would definitely allow you to play 1600x1200 smoothly. Or even just overclocking..., maybe even without any of it, you'll just have to try it.
Call of Duty: United Offensive should be a breeze on any of the current generation cards. It still uses the Quake 3 engine (OpenGL-based). The 6600GT/6800 are very fast at OpenGL.
Originally posted by: Cheesetogo
A 6800 is hardly any better than the 5950, so if you want tor un 1600x1200 with high settings, you need at least an 6800gt, which can be had for around 300 dollars. The 6800 will not be much different from the 5950, and will not be enough.
Huh? Even the 6600GT puts the FX5950 to shame, especially in shader performance. Look right here, at 1600x1200.
http://www.xbitlabs.com/articles/video/display/geforce6600g-games_11.html
A 6800 slightly surpasses a 6600GT, though with lower clocks, it has 12 pipelines and a wider memory bus. It's worth noting it's an excellent overclocker as well. Looks like you are a modder, so you should have some fun with the 6800.
You could wait five days when G70 comes out, and see how 6800GT prices fare. Also, I don't think you need any more than 1 GB of memory. With that extra money for RAM, get a 6800GT instead. All my games, Wolfenstein: ET, Half-Life 2, Battlefield 2 Demo play admirably with 1 GB of memory.