PSU requirement for 2x MSI GTX 760 OC SLI

[Cheatah]

I"m pretty new to building my own rig, but I'm hoping to get some feedback. I currently have 2 MSI GTX 760 http:// and I was wondering what would the minimum PSU to run with SLI enabled. I currently have a 550W PSU and trying to run a couple of games with SLI enabled either gives me a black screen with no response from the keyboard or crash while I'm playing. I don't know much about computer to be sure it's the PSU, but I'm leaning towards it. Any feedback is welcomed, thank you.

 

[jbaker22]

This should tell you what psu you should buy.

http://powersupplycalculator.net/