I humbly suggest that you contact the manufacturer of card in question... you may already have done so.
Unfortunately I can't give any better advice than this obvious bit. I have never cared much for games and my Mac plays Nanosaur quite well enough for me using a Rage Pro, standard on my beige G3 rev2 MT @ 300MHz. An upgrade to me means CPU or RAM, standard graphics acceleration is sufficient for my needs.
And please accept my apologies for such a lame post, I am a new moderator for MacNN and I will attempt to stir up discussions from time to time!!