heres a better choice maynn...get a 7900gtx on ebay 300 bucks..per awesomeness
Ew. You can get a brand new X1900 XT for $200 on newegg that will stand toe-to-toe with a used 7900 GTX that costs $100 more.
But as far as the poster, keep your 7950 GT. It's a fine card, especially for what you paid, and it's not worth it to go to a 7900 GTO from there...