I've moved on to PCI-E but my old rig had an XFX GeForce 7600GT 256MB 128-bit GDDR3 AGP 4X/8X which as previous posters have noted will run SH4 but you'll likely need to dial back some graphics options.
But you're in luck because despite AGP going the way of the buffalo there is a very robust AGP board still in manufacture. Not sure the specs on your Mobo but here's the link:
http://www.newegg.com/Product/Produc...82E16814131161
Good Luck!