BE WARNED: Those high-end graphics boards you mentioned are for 3D MODELLING! That means real-time updating of WIREFRAME MODELS!
They are NOT used for texturing. The best boards for moving texture-mapped stuff around the screen are the nVidia offerings.
In a recent net magazine test, I read that running Q3A at 1600x1200x32, max detail, the FireGL ran at 10FPS! and the GeForce2 Ultra ran at about 30fps! I am not certain on these figures, but they do sum up the difference in targeting.
However, in moving a 1 bazillion (or something) polygon model around the screen, the FireGL was about 60fps, and the GeForce2 about 10!
Note: Do NOT quote me on these figures! They are from memory only. They may not be accurate, but I am pretty certain that the differences in performance are. But still, I am not responsible for what you do. Do some reading (check the archives at www.tomshardware.com)..)