If ya tryin to keep the budget down, compare the 560 Ti (900MHz) and the 570 and consider if its worth the extra cost.
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 OCZ ModXstream 700W is not going to support a build with two GTX 570s. This is because it doesn't have enough PCIe connectors (four are required, the MXS700 only has two) and you would be using up all the 4pin peripheral connectors to use adapters.
$40 cheaper then your best quality combo which #2
$10 cheaper then your 2nd best combo #4
$18 cheaper then your #1 non-modular offer
XFX PRO750W XXX Edition psu is a higher power and higher quality unit then any unit you've listed
#3 combo features a terrible psu that's to be avoided at all cost/max power is under 600W = POS
The case combo features another POS power supply .