Well, I was running the same CPu with a 6600GT and the CPU was slowing the whole system down, when I got a new CPU(Core 2 Duo), Gothic2 for example, ran perfectly fine, using the same graphicscard, so my guess is anything over an NVidia 6600series card would be a waste of money because your CPU would be the bottleneck anyway. If you get a new system, you won't want to use that AGP midrange card anymore anyway so I would go for a 6600GT from NVidia or Radeon 1600Pro(they are roughly the same, depending on the game).