In case you missed it, a couple days ago NVIDIA outed the Fermi Quadro 4000 Mac Edition video card for Mac Pro users. The card packs a punch with 256 CUDA cores, a 256-bit memory interface and 2GBs of memory (I remember the day I got excited by a video card with 16MBs of memory, though, sorting out the right driver was always a bit of a problem so maybe nothing's changed there).
NVIDIA says the Quadro 4000 will deliver "...excellent graphics performance across a broad range of design, animation and video applications." Especially if you use Apple's Final Cut Pro, DaVinci Resolve, Autodesk Smoke, Mathworks Matlab and Adobe's Creative Suite 5.
However, this kind of performance doesn't come cheap. The Quadro 4000 has a suggested retail price of $1,199. It may be a little on the expensive side (especially compared to its PC counterpart), but then again, this card isn't for your favorite FPS title. You'll see this card fly when designing 3D graphics, HD video editing and rendering those rather large video / image files. The perfect holiday gift companion to go with that new Mac copy of AutoCAD. And if you've got the new AutoCAD for Mac then money's not really a problem for you anyway, is it?