Dual GTX 580 Lightning or GTX 680?

Allright the title may lead you to think that im out of my mind as a dual MSI gtx 580 Lightning is clearly better than a single GPU even if it is one of the high end 600 series, but youll see my point soon enough. so I'm planning on tricking out my rig to max the hell out of Star Citizen when it comes out and I am waiting on my motherboard, cpu, and RAM choices (because new architectures like Intel's Haswell will be coming out later this year and Star Citizen is at least 2 years away). I have hard drives and ill get an SSD to boot off of and everything...but I'm wondering what i should do about my graphics cards. See, I already own one 580 lightning and SLIing two of them would be badass! My 700 watt power supply though does not have two extra 6 pin power connectors and even if they did I probably wouldnt have enough juice to power those two cards, a high end I7, multiple hard drive,s and fans everywhere. I have the option of buying a 1000-1200 watt power suppply  ($200-$250 for 80 plu platinum) and getting a used 580 Lightning ($400 where I saw it) or simply buying an EVGA 680 FTW and hoping I have enough power. when i do the numbers in my head It seems I'm saving money just buying the 680, but is the performance I get from the580s worth it given the price I have to pay? 

 

TL;DR 

buy a $400 GTX 580 to SLI and a 1200W power supply or keep my 700W and get a 680?

 

Thanks for your help guys!

Always get the single most powerful card you can, and if you can wait a bit the 700 series should be out soon and that will give you even more performance on a per card basis

Thats my thinking...it seems way too soon to buy components for a build that will be finished in two years =D