AGP cards now are very rare, they're sort of endangered species that will soon be extinct.
High end NVidia AGP's are rare and near extinct, but that's about it. It's not hard to find good AGP cards, but it's hard to find one that is as good a bargain as an equivalent PCI-e card; AGP typcially cost more now.
OP: Best to worst, see what you can find in your price range.
X800 pro / X800GTO
Radeon 9800 pro 128MB (256-bit memory interface)
Radeon 9700 pro (256-bit memory interface)