I realize that you stated that you are a student and are looking for a faster processor, but if you are looking to increase video game frames then the first thing to consider is a graphics card upgrade. You can upgrade your processor but money spend on a faster graphics card will net more frames. Socket 939 processors are getting harder to find but faster PCIe cards are getting faster for fewer dollars.
Here's a recent graphics card test from Anandtech which has an ATI HD 4850 putting in some decent numbers. If you have a preference for Nvidia card then they are expected to respond to ATI's new card in early July with something in the same price range with higher performance.
http://www.anandtech.com/video/showdoc.aspx?i=3338
If you feel that you absolutely have to move to a faster socket 939 processor then I would move quickly because although they've dropped in price they are also getting harder to find.
Here