We have seen excellent graphics performance from the Diamond Fire card, and from the Accel Graphics AccelEclipse. Both cards use the Mitsubishi DMA/RealImage engine, and are both very expensive (2-3K).
Before investing in a card like this you might want to wait for the next generation of cards and cpu's that offer AGP2 and 100Mhz PCI bus.
Another strategy that you might want to deploy is using two machines, one for audio, the other for graphics, and use the netsend and netreceive objects to share data between them.
Drop me a line if you want more information. -RS