I already have 1 8800gt, so should I look at getting a second to run in SLi or should I wait and get a better single card like a gtx260 or HD4870? I'm curious as to which setup would yeild better results. My system specs are in my sig.
- Do you care to spend a LOT of money for the bigger card?
I'd say go for the 2nd 8800GT: Cheaper than ever and still giving good performance.
Now, i don't know much about nVidias cards, so i don't know if your PSU would hold up with 2 8800GTs. If it can't, then see if going for a GTX260 costs more than the 8800GT + what-ever-watts-you-need PSU. (added)
On a side note: I have a friend with a rig close to yours (already 2x8800GTs and 900W PSU) and i can tell you it's a fine machine.
A quality Earthwatt 650-watts power supply should be enough to power 2 GTX260's in reality. I would definitely go for the second 8800GT, though, only if you're playing at 1680x1050+ resolutions... anything below that would be a waste.
Go for the second card. It's alot cheaper and the drivers for multi card setups has been improving. If you can afford it a 260 would be nice, after all a faster single card solution is usually better than dual card setup. Going SLi means there may be a few games you want to play that prefer a faster single card, like a 4870 or 260, but by and large you'll get good SLi performance out of the more popular games. Check the charts here and on guru 3d to see if dual 8800 GTs will perform well in the games you care about.