hmm,the most better one is gtx580 and can beat these both gtx570 and 6970 and yes gx750 is enough even for sli also.but if you want to save money then gtx 570 is a lot better.i am not sure with xfx brand the only thing i know that is lifetime warranty but don't care about it gtx570 or 580 had better overclocking,better performance.
Well to be honest these are Reference Design Video Cards so they do not offer the Cooling Capacity Double Fan Designs Design Video Cards offer so they may suffer from overheating issues, Go with MSI or Gigabyte Video Cards.
In the current situation the order in wish these video cards are currently are more powerful are GTX 580> GTX 570> Radeon 6970 so if you have enough money to go for a GTX 580. I would go for it since it will max almost anything in 1920x1080 over 60 FPS at 1920x1080 with just one card solution.
Also the Cooler Master GX750W offers enough PCI connectors to support Dual cards for any of the Video Cards you have selected, But if you're wishing to go SLI with one of these cards I'm guessing you will need to OC your CPU to get the most out of these cards so go with a more Reliable Brand other then CM in Power Supply's. I'd recommend Corsair HX850W if you wish to go the GTX 580 Route OR a Corsair HX750W if you go the GTX 570 and Radeon 6970 Route.
Remember, it's not about turning it on and not having it crap out. It's about providing stable voltages under load for both overclocking stability and long term reliability. I use 950 watters minimum for twin 580's, 850 min for twin 570's and 750 for twin 560's though if pushing the latter to 1000 MHz, I'm more comfy w/ an 850.
Using the extreme PSU calculator w/ twin 580's, and 5.0 GHz CPU OC, 5 USB, 1 FW, 5 fans and card reader, and 15% capacitor aging, I get 886 watts
Using the extreme PSU calculator w/ twin 570's, and 5.0 GHz CPU OC, 5 USB, 1 FW, 5 fans and card reader, and 15% capacitor aging, I get 869 watts .... that number seems a bit high....I'd have expected maybe 785.
Using the extreme PSU calculator w/ twin 560's, and 5.0 GHz CPU OC, 5 USB, 1 FW, 5 fans and card reader, and 15% capacitor aging, I get 729 watts
And that's with no overclocking on the GFX.
As for what to choose, if the target is SLI, it's hard to argue against twin 900 MHz 560 Ti's if the benchmark is frames per dollar. Their 862 fps score (48 cents per frame) in SLI is marginally behind the twin 570's which get 11 fps more at 873 fps (73 cents per frame) and surpasses the twin 6970's by 37 fps (825 fps @ 87 cents per frame) in Guru3D's testing. You can easily take the 560's further to 1000+ Mhz whereas the 570 has not shown that kind of headroom. The 580 is the undisputed champ but at 101 cents per frame in SLI it's abit of an investment.
Guru3D uses the following games in their test suite, COD-MW, Bad Company 2, Dirt 2, Far Cry 2, Metro 2033, Dawn of Discovery, Crysis Warhead. Total fps (summing fps in each game @ 1920 x 1200) for the various options in parenthesis (single card / SL or CF) are tabulated below along with their cost in dollars per frame single card - CF or SLI:
The 570 has had some issues with its VRM ..... a web search will find you many stories of fried cards but you'll find most of these resulted from exceeding manufacturer's published voltage limits. Can't fault the manufacturers or the design for that except to say that enthusiasts are somewhat spoiled by "getting away with such tactics" many times in the past with other cards. The 560 and 580 VRM's do seem to be a bit more "robust" given the lack of instances with these cards.