And if you upgrade, don't upgrade to an AGP mobo, get a mobo with PCI-E . . . AGP uses direct traces to the "northbridge" area of the chipset, and is physically closer to the CPU, but PCI-E has much greater bandwidth. Remember, AGP is overglorified PCI with direct traces, all further versions of AGP (3.0 is the current standard) are built on the same limitations with greater bandwidth. PCI-E is designed primarily to replace the PCI spec but replacing AGP was kept in mind.
Think of it this way. PCI was the defacto standard since the pentium 1, all the original graphic accellerator cards used it. When the need for bandwidth outstripped PCI's abilities, they made a band-aid called AGP. AGP worked for a while, but it is still a band-aid. PCI-E is an overhaul of the whole bus system which hosted both PCI and it's bastard offspring AGP.
Any, and I mean ANY, of your upgrade options must include PCI-E or you will only replace your mobo again. Upgrading your PCI card will be useless.