Those cards are for view-port editing only pretty much. They offer the ability to have neat things like anti-aliased lines. They work using standard OpenGL/D3D drivers like most other cards.
The professional cards accelerate things like large wireframes & anti-aliased lines. While scrapping speed optimization for games. Also leaving large chunks of driver support missing for games.
Gaming cards are more tuned for gaming... ERrmm yeah...
As for final renders and effects in Combustion, a pro card will be no different than a gaming card since those are mainly done by the CPU. Though some of Combustions effects are done realtime in openGL, but with those things you wouldn't notice much of an improvement with a pro card.
http://www.lostcircuits.com/video/3dlabs_vp990/6b.shtml <---about that card...
http://www.lostcircuits.com/video/3dlabs_vp990/6c.shtml <--max payne with that card(not pretty)
http://www.digit-life.com/articles/prof ... date1.html <---about the Quadro line of cards...
-Klinky