For maya, the ti4800 is a better bet *if* your willing to use the softquadro drivers(which effectivly turns the card into a Quadro 4 990).
If not then possibly the firegl, though its based on very old architecture ( the radeon 8500) and I've heard many bad things about ati's so called "workstation" drivers with maya on various forums and lists.
Personally I wouldnt trust em though thats just my opinion.

nem: the ti4800 is the new agp 8x card. the 4600 is 4x.