as far as i know 7950gt in sli is better than a single 8800gts. but u will not have a directx 10 compatibility though. i say u wait with this sli setup and go for something better later cause your current gfx solution is sufficient for now. let dx10 games to come out and see what happens. and once new cards enter the market then decide. hope i helped.
in this high resolution case, sli would be better as sli and crossfire are known to give good performance in high resolutions. and even if u decide to buy 8800gts then go for 640mb version as it will perform better than the 320mb version.
The 7950Gt in SLI is a remarkably good performing video card.The dual card setup really enjoys high-resolution gaming.Unfortunately for you,you're unable to get SLI working in your computer and are forced to look at upgrading to a single high-end card.I'm assuming you have the latest motherboard bios and latest drivers for your cards and that every other option has been tried including RMA'ing the board.If this is the case then I strongly suggest you look at the 8800GTX and not the GTS as the GTX is superior to the GTS in everyway.It's your only logical choice as the two 7950 setup in SLI outperforms the 8800GTS by a bit of a margin,leaving you with the GTX version as the only way to go.Just get the base version and you'll still be amazed at the perofrmance of this card.Goodluck.
Just check out the VGA charts here at Tom's. They have benchmarks for the 7950 GX2, which is close enough to your setup (assuming SLI is on) as well as the 8800 GTS. I looked them over briefly, and it looks like the SLI setup is best for high resolutions (greater than 1600x1200) while the 8800 is better for anything less than that.
Look, If you already have a 7950GT SLI system, don't bother. You have a killer system right now. Why upgrade? You should upgrade when your system starts to lag on modern games. You have a bit more horsepower than a 8800GTS, which is in the top three most powerful cards on the market. Upgrade when your 7950GT SLI becomes as fast as a X1950pro with today's games. (Assuming you're gaming at a high resolution)
Thanks for all the replies. I wish I could get SLI working. I have a asus 8n sli mobo with 2 7950's. Both work when i install just one. I'm using vista ultimate. Tried drivers/uninstall/re-install..device manager shows both cards but SLI just won't work. With the game lost planet I'm getting about 17fps in 1920x1200.