Video card compatibility in OSX


I am the law!
I'm looking for video cards for my mac but they have to be compatible with OSX. I need 4 total.

Right now I have an AGP 16MB ATI Rage Pro and a PCI 16MB Rage Pro. I guess ideally I would buy 2 more PCI Rage Pro's but I have no idea where to find them. Haven't found any on ebay. I have found Voodoo 5 PCI cards, but I have no idea if it will work in OSX.

I would like to replace the AGP one with a 32 or 64MB card.
Any suggestions?