Power Supply Suggestions!

[ErikM]

Hey everyone, I have been posting a lot on these forums lately, but I've got to say, you're all quite helpful!

So I am building a new gaming PC quite soon and this is the build I seem to have come up with a pretty satisfying one in my opinion, the only problem is that I'm not sure which power supply to get. I'm not sure how many watts I ACTUALLY need. I don't want to go overkill like some people.

Here is the link for my build:
http://pcpartpicker.com/p/3EIwF

I have one gtx 770 now, but I most likely will add a second one for SLI in the future, which is why i need help. I cannot find a straight answer as to what wattage I need for two 770's.

I'm looking for quality brands like Seasonic, Corsair, Rosewill, etc. I'll link some below that I was looking at. Thanks in advance and any answers and opinions will be appreciated!
(Also I'm looking for 80+ Gold or higher, I want a lot of efficiency.)

Seasonic SS 750w:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817151087

Seasonic X 850w:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817151102

ROsewill HIVE 750w:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182133

Corsair HX 750w:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139010&nm_mc=AFC-C8Junction&cm_mmc=AFC-C8Junction-_-na-_-na-_-na&cm_sp=&AID=10446076&PID=3938566&SID=

 

[i7Baby]

Use a power supply calculator - http://extreme.outervision.com/psucalculatorlite.jsp

2 x 770 pc should use about 850W, so go for your Seasonic X 850