I have not been able to find any game benchmark results for Quadro cards (at least, nothing more recent than one published in 2000). To me, that says that such cards are not meant for this usage, which probably does not bode well for their performance.
I do remember reading a review of such cards a long while ago, I think it was on Tom's Hardware, where the article said more or less that, while the Quadro line is a stunning performer in rendering static scenes, gaming is not its forte.
Last nail in the coffin, so to speak, is the fact that on Nvidia's site, the Quadro is touted exclusively for work applications. The word game is not even present on the page that talks about Quadro line.
Finally, I'd remark that a Radeon 9800 is a better choice than the FX line. If you really want to go Nvidia, go for the newer 6xxx generation. As you can see
here, the Radeon 9800 XT does much better than the FX 5950 Ultra, but both are squashed by the 6600 GT.
On Shipzilla, a
5950 is apparently hard to find and has a going price of $438 to almost $600. If you're ready to spend $600, you can get an FX 6800 Ultra, and there isn't much better on the market at this time.
For less than $300, you can get a 6800 GT, and a 6600 GT is going to fetch $212 at the most. Of course, these are models with 128MB of RAM. You might think of getting the more expensive version with 256MB - if you're a serious gamer, it will be worth it.
Forget the 5950, its performance is not worth the price today.
Pascal.