that is a great psu read some reviews here:http://www.hardwaresecrets.com/article/OCZ-Fatal1ty-750-W-Power-Supply-Review/1019
Well here you check the SLI certified PSUS list:http://www.geforce.com/Active/en_US/en_US/pdf/PSU.pdf
And since your psu can handle a 570 SLI
570 consumes ~219 W
6970 consumes ~207W
so yes it will probably handle it safelly, i just don't recommend overclocking any components, run them with default clocks but even overclocking it should handle perfectly since it is certified.