I have never heard of a radeon 7500 mac OEM video card. I know AGP4X cards will underclock/whatever when used in an AGP 2x system.
Whatever you do, don't try a GeForce ANYTHING card in your Sawtooth with Panther. It will not work (do a search).
Otherwise, I still cannot answer your question. Search the Xlr8yourmac.com forums for more info on your question.