One further tidbit for you, Cox orange - I believe that the rare GeForce4Ti (4600) OEM Mac edition video card will function with full hardware acceleration under OS 9. It is roughly equivalent to the Radeon 9800 in power, but was never offered as a retail card and is therefore rare and expensive, (though flashed PC examples are cheaper). It is probably the fastest OS 9-compatible card ever made.
It does not, however, support Core Image in OS X, so if you plan on running both OSs your best bet is still a combo of the Radeon 9800/Radeon 9200 PCI cards.
Better off with the Radeon 9800/Radeon 9200 suggestion if money isn't a problem. The Geforce4 Ti 4600 was the best card in its day (2002) but the 9800 pro offers about twice its power. Unless you want to build up the best OS 9 gaming rig