for performance now get the gtx 480
make sure you buy a good brand psu (corsair ,seasonic etc)
avoid coolermaster at all costs
just keep in mind the temps and power consumption for the 480
Here is a rather thorough list of power supplies, the good and the bad. The ones in tier 1 and 2, and sometimes 3 are good power supplies. I would only recommend 1 and 2, but that's just me.
If you want the power now, the 480 is the way to go. Sometimes AND ONLY SOMETIMES people are not happy with how the SLI is working in their system.
EDIT: That being said, the 560Ti right now should be able to play BF3 on pretty high settings. On singleplayer on ultra, my Radeon 6950 runs it at 55 or so fps, and mine is about 1-2% percent faster than a 560Ti.
Multiplayer is a different story. Its much more CPU based.