I am using an ATI X800XL. Low price (not a top of the bill card, but quite fast anyway). I use it with femap, which has a nice renderer, and it works very good compared to the NVidia I used before (4200Ti or something). Note that most new generation card use PCI-express interface, and not AGP
But, as Greg Locock mentioned: any standard graphics card can not possibly be the bottleneck of your workstation.