So are you saying that even the GeForce card is slow PCI bus it's still would be better than the faster AGPX2 Intel card I have? So does that mean any PCI card even the lower end ones still are better than the AGP2X Intel card? Or are you saying that only the GeForce 9500 GT PCI is better than the AGP card and others that are cheaper PCI cards are not as good as the Intel AGP2X card onboard this machine?
I've researched this a little since I answered your Q's yesterday.
Despite the slow PCI bandwidth the PCI GPU recommended by Foothead and Atomic Rooster will perform better than the 810i on board GPU your currently using. See the 810i GPU is a very simple on-board solution and is easily bettered by PCI cards simply because of the better GPU core and it's own memory.
So forget the bandwidth speeds of AGP/PCI here. The 810i on board GPU is no match for the 9500GT with its 512MB RAM.