Like most high end video card setups, your brain is telling you that you shouldn't spend in excess of $1000 and buy this setup. It tells you that you could get performance that's good enough with cheaper setups. You're heart, though, just wants to dive all in and get all dirty with your new VGA setup.
Like most setups, there's very little overall value here when you talk about the FPS you get for the dollars you're spending. The bottom line, though, is that the GTX 580 in SLI is not just fast, but has no problems playing any game at max settings.
Averages in excess of 100 FPS at 2560 x 1600 under games like Lost Planet 2 and in excess of 80 FPS in Aliens vs. Predator just paint the picture of what you're getting here. The setup isn't about justifying the money you spend, it's about getting the most FPS you can get.
Of course, move to Surround Vision and Eyefinity and increase that resolution three fold and you're going to be able to bring these cards to their knees. More AA, more AF, more resolution, more monitors, the GTX 580 SLI setup is all about more, more, more!
In the end it's really all very simple. If you've got the money and you demand nothing but power then this is the kind of setup you should be looking at. If you wanted to go SLI GTX 480 but got scared off by the heat and power draw, this is the kind of setup you should be looking at.
When you combine the fastest single GPU video card on the market with a second one, you blow out the bank account and blow out the FPS. I can understand why people think that it's crazy to spend so much on a VGA setup like the one we're looking at today, but this kind of setup is just all about performance and making sure your games can look as good as they can and run as smooth as they can.
I very much feel what separates a good product or setup from a great product or setup for me personally is; would I use it? - There are plenty of good products out there that I wouldn't use myself; the GTX 580 is a prime example. I use three monitors; I would need two cards to run three monitors, so for me a single GTX 580 is a moot point. The GTX 580 in SLI, though, apart from the lack of DisplayPort is something I would use, and thoroughly enjoy on my three monitor setup. The chances are if you love games, love high FPS, love high detail and don't mind spending the money, this is a setup you want, if not already have.