Thanks. It seems that Ati 4870x2 and GeForce GTX 295 were most popular at the time than AMD 6990 and Geforce GTX 590. Am I wrong?
The upshot is that you get around the ridiculous premium NVidia charges for licensing SLI (one of the main reasons MB costs have become completely ridiculous). The downside is that modern NVidia boards are so awful in terms of efficiency that this thing gobbles something like 400 watts, and still fails to deliver good results. PLEASE, bring back true SLI (scan-line interleaving!)
I opted for a dual GTX 470 as an alternative. You can get a pair for about $330, beating the GTX 560ti and killing the GTX 580 on price.
Looking at those charts, the 6950 Xfire was looking pretty darn good!
I used to have a GTX 295, and also tried 560 Tis and 480s in SLI. Definitely prefer my single 580.
Interesting. There is more power-horse for 2x6950 CF but power users mostly prefer ONE GTX 580 for almost the same price at this time I'm typing this