Graphics card upgrade advice for XP2800

Never played the game but it seems lousy performance goes hand in hand with it. Look how beastly cards perform in it:
http://www.gamespot.com/features/6163248/p-6.html

It also shows that the game is quite CPU bound, not helpful with your XP2800+
http://www.gamespot.com/features/6163248/p-7.html
And they say don't even think about playing it with 512MB of ram

Even though a new GPU like an X1650 pro or 7600GS would put your system above minimum spec, I would not expect the best gameplay out of the rig. Resolution and details will have to be quite low I'd think. But like I said, I have never played it so maybe someone with similar specs to yours can give you a better answer.