I don't think I can stress this enough.
[YOU DON'T USE AN AGP CARD. YOU'RE GRAPHICS ARE ONBOARD, THUS, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING,
ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING,
ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING,
ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING,
ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING,
ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING,
ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING, ANYTHING,
--- IS BETTER THAN YOUR CURRENT ONBOARD GRAPHICS.
Edit: You've lost the concept:
PCI and AGP are simply doors, if you will. PCI is the door to a small coat closet, while AGP is the door to your bedroom. PCI-E is a set of double-doors. The interface is for BANDWIDTH. Speed, yes, but mostly bandwidth. The GPU is what you should be looking at - The strength of the GPU. Bus doesn't even matter.