I've had a AMD Radeon card in my PC for 2 month - Vue had to switch off a few things (like background draw for instance), because it wasn't a Nvidia card.

AMD Radeon cards don't use CUDA - that's a NVIDIA specialty. Radeon cards use something close, but not as strongly supported as CUDA, which is called OpenCL !

After getting the new Nvidia GTX 680 (single GPU) card, Vue works great with this graphic card. It doesn't use the GPU for rendering (CPU), but it supports (since Vue 10 or was it Vue 9 ?) the calculation of Anti-Aliasing using the GPU to speed it up. Important, too, for sure, is the onboard RAM amount. They've got at least 2GB , which will help with displacement-mapping and heavily loaded scenes.

Surely the 690 version (double GPU) is for sure a monster card for speed ! The 680 is already very fast, but logically a twin GPU card like the 690 beats it by huge steps. The fastest card so far - but really expensive !

The now to be released GTX 670 card is just a little weaker then a 680 (first tests shown that), but cost wise it spares you quite a lot of money for barely loosing too much speed compared to a 680 card.

So - 690 is for sure top-notch - but the price with more then a 1000$ is quite something - unless you don't have a problem to spend ...

Sure - Quadro cards are pro cards for CAD or stuff like that - but those are not as versatile in their use and strength with everything 3D (...like running stuff like Skyrim game or others) you like to run on a PC besides 3D software like Vue,3dsmax and such.