AGP graphics card

BS"D
I just bought a used 20" iMac, 2.16 Intel Core 2 Duo, OSX 10.4.11, FCP 4.5. When I try to open my FCP, the computer tells me I need an AGP graphics card. Which card is best for the computer?

BS"D FYI - Went into a Mac forum and the warning about the AGP graphics card is bogus - my version of FCP wasn't working together with the new system. I upgraded to FCP 5 and it's gone, and I'm able to edit again.