8500 or 9000 are the best (fastest) ones with 3D support in MorphOS.
These typically come with 64MB video memory
To be precise: The 8500 always is 64 MB (there are no Mac ROMs which support more), but the 9000 is also exists as 128 MB version. So a 128 MB 9000 really is your best option.
Aren't there tools that allow you to overwrite the video bios for a vanilla ATI card with a Mac specific one? IIRC, that's the only difference between cards released for PPC macs and their generic PC counterparts.
Well, in fact there are more differences. Most (if not all) AGP Mac cards have a proprietary Apple display connector which features USB leads and other stuff. They also have an additional connector in front of the AGP part. That aside it is true that you might be able to flash your PC ATI card. If it has 128k flash ROM... many PC cards only have 64k. There are also hacked 64k Mac ROMs. But as you can see it is all not that easy, you have to be lucky to find a flashable card and be lucky that it works correctly afterwards.
