Ok I have a few questions..first of all I'm currently running two Nvidia Geforce GTX 560. Prior to that I was running two GTX 460s. I have an Alienware Area 51 computer and they replaced both of my GPU's do to heating issues that were causing artifacts while playing games. However, even with the new cards, I'm still have heating issues. I was told that the problem is the nature of the SLI configuration and the fact that more work is placed on the "primary card." Also, I guess when they first designed this system, they didn't place enough fans or didn't place them low enough in the system so the cards aren't getting the best cooling. I received the recommendation to go down to a single GPU, and my question is basically will I see a loss of performance? My concern with going back to one GPU is the fact that I also run two monitors, and was thinking about adding a third. I definitely want to run two for sure, the third I can live without. Will running two monitors on a single GPU be a bad idea? Is there a brand that is better with running dual monitors? I don't plan on doing gaming across the two screens. I usually play D3, Wow or SC2 on my primary 25" monitor and use the second monitor for browing/itunes/other programs. Basically my choice is to keep the dual 560's, or upgrade to a single GPU with 2gb or maybe 3gb. Also, I'm pretty sure my MB only supports PCI Express 2.0, i don't think it's new enough for 3.0. How close would the GTX 580 be in quality to the 560? What do you guys think?
Having a second monitor open for browsing is a minor load on your GPUs. It's not a big deal at all. You will certainly see a loss of gaming performance with only one 560 (are they 560s or 560 Tis?), but you'll still be able to play any game on mid-to-high settings with 60fps. You'll still be able to max out those three games if you've got a decent processor (do you?).
The 580 is much better than the 560. It's also much more expensive. It's not the latest generation of cards, though, so I'd pass unless you've got some special used source. As I said, though, you'll max those three games with just one 560, so wait on upgrading unless you plan on starting to play more demanding games.
The Alienware case, it looks cool but not enough air flow. Ary you using a program to monitor your temps like MSI Afterburner? You can watch your temps on an overlay on you monitor while playing games.
Also you can set your fan speeds to go faster when the temps go up so does the fan's. You can watch your fps and your GPU usage all at the same time. This month they are releasing the new 660 Ti and the 660.
If you want to upgrade then choose that card or cards to go with. Using two cards does not cause the first card to work harder it works a lot easier because the second card picks up and helps.
Two cards will cause higher temps but that is a given. One nVidia card will run two monitors without problems inorder to run 3 monitors you would need two cards. AMD cards you only need one to run 3 monitors.
I will will link you to the MSI Afterburner program if you don't have it. I will link you to a few other monitoring programs. They come in handy and I know for sure because I use them my self. Good luck to you.