A 7800GT? Not worth it. X1950 Pro? Thats a decent upgrade.
Personally I was waiting for the 8600GTS, but now that the 320mb 8800GTS has hit the $250 price range thats your best choice. I just ordered one this morning.
It depends on your budget. If you want to pinch every penny you can, you could possibly get a cheap x1800/x1900 higher end card to hold you off until the 8 series refreshes come in(or the refreshes of the refreshes). I know a person who is still pissed off because he bought a 7800gt weeks before the 7900gt came out. I still taunt him by reminding him that he could have easily purchased the performance of a 7800gtx for the same price.