Well, to muddy the waters a little more, in my experience I receive fewer video card-related calls on NVIDIA Geforce than I do on ATI Radeon. My personal recommendation is to find any card where the second number in the model number is a 6 or higher. The 6 cards are all in their high-performance gaming line. You can see from this graph that most of the Geforce *60 cards rank pretty high in comparison to other cards out there:
http://www.videocardbenchmark.net/high_end_gpus.html
I would avoid Quadro and FirePro lines though as they are not optimized for gaming. They are engineered with computation in mind. The high-end models seem to work most of the time but it's hit or miss. If 3D modeling and rendering are your primary focus, stick with a gaming card from the Geforce or Radeon lines.