Well, when looking around on Froogle, be sure to choose a 6200 with at least 256 MB of RAM. Some of the same model were released with 64 or 128 MB.
Here's an example of what you're looking for. The seller has a good rating, and it's a good price, too.

I've got the FX5200 it does the job so far, but I definitely want to upgrade to deal with the newer games coming out. I've been thinking about getting a GeForce 6100 onboard, a friend told me you can set how much of your RAM you want to dedicate to graphics memory. I've got 2gig RAM, so I was thinking of setting 750mb to graphics and the rest for RAM.

Would that be worth it?[/b]
I honestly don't know in that case. It might impact performance, not having dedicated video memory on the graphics card, but I've never worked with that sort of thing, so it might not, too.