Two 580s in one card my ass.
If you want two 580s in one card I suggest you get a 900w PSU with at least 62amps for the ASUS ROG MARS II
Shit costs 1k.
Plus minimum PSU wattage for a single 580 is 650w and it requires 42 amps.
By the way, don't ever get Sabertooth P67, there is a start up problem.
Get some Z68 chipset motherboard.
It's even cheaper.
Your build is so much like mine.
I had a cooler master V6 GT, now I use a liquid cooler.