Quattro cards are are generally used for things like AutoCAD, where it is really important to have things be as accurate as possible. I would rather see you spend your money on a high end Geforce than a Quattro. A Geforce card is better suited to game development, as it is closer to the type of things that your average client will be using.

Actually the difference between Quadro and Geforce is that they use some functionality that will never be in a game.
The Quadro supports stereoscopic viewing. This may increase the gaming experience, but DirectX 7 didn't seem to have success introducing it, since MS dropped it's support quickly. Also Quadro user's would be the only ones who would get stereoscopic support.
On the other hand the Quadro supports better windowed clipping. GeForce cards suffer big performance hits when multiple 3D window instances are active and start overlapping each other. Games run on a single window.... and in fullscreen, which avoid the problem. This Quadro advantage suits perfectly for intensive use of 3DS Max, Maya, AutoCAD or alike programs.
Also the difference between NVIDIA's low-end vs high-end (i.e. 6200 vs 6800) is not feature support. They will both have Shader Model 3.0 (or the latest 4.0 for 8xxx cards) the difference will be on it's speed.
You may want to check http://www23.tomshardware.com/graphics.html

PS: I own a GeForce 6200 256 MB AGP 8x and so far the card's speed was the least of my problems. And also most games run fine (by meaning "most", I mean that the latest games can't be used with at max quality)
As far as game development, CPU starts becoming a bigger issue rather than GPU (when compiling, testing AI, using the debug version)
When debugging and using many advanced tools, RAM usage starts growing exponentially.
CPU is not important for end users, but it is for developers, since we first create, then optimize (also productivity increases if you press F7 on VC++ and the program is instantly built; instead of waiting 1-5 minutes).

Hope it helps
Dark Sylinc