Ok the 7900 GS stock is just as good as a 7900 GT stock. The frame rate loss I think is 1 to 2 fps in most games. I managed to overclock the card to 700/1700 from 500/1380 with some minor volt modding which gave me to 2k more in 3Dmark05.
Also I think the prices of the 7900 GS kept its low prices where are the x1950 pros prices sky rocketed. 159.99 after rebate for a evga 7900 gs vs 179.99 for a Diamond x1950 pro (Never heard of Diamond, would have put Sapphire or ATI instead but those versions cost more and people would complain and the Sapphire versions have been out of stock for a while.)
i3 540 @ 3066 MHZ
4GB DDR3 1600 1T 9-9-9-28
HD 5750 @ 850/2400
Antec Lanboy Air