It wasn't that long ago that the Mac video card flashing scene was alive and buzzing with activity. Now, it seems dead. A popular forum for those working on such things has been down for some time and it doesn't look like it will ever come up.
I don't think they ever got any ATI card beyond the 9800 working. I think that had the Geforce 7800 working, though.
My B&W G3 is happily humming along with its 'ole Radeon 9200. The actual Mac Edition too. Woo woo. Good days.
Hey, the 9700 Pro is more than enough -- I do intend to flash mine one day, once I've no longer need of it in old PC gaming machines. It'll be quite impressive running in a Quicksilver mac, I'd bet.