Here's what you do. Save up cash, get a job maybe and get a new rig/computer. The newer ATI cards have compatibility issues with other games I would not recommend just buying one.

The reason why I'm asking you to do this is because AGP is pretty much obsolete. Buying an AGP card "now" would mean your wasting cash. Do not give your computer life-support if its hardware is already considered obsolete.

I recommend any mid-range multicore processor from Intel, 4 gigs of ddr2 / ddr3 ram and an ATI Radeon 4850 if you're going for ATI / Nvidia 9800GTX if you're going for Nvid.

About the graphics solution.. You can wait to see whats going to sell this year from both companies then only buy or you could just get whats cheap on the market now.

Have fun building your rig.