For a Single GPU - I would buy the EVGA 1200W P2 1200 Watts
They are great PSU I have several
If your going to go crazy in OC or multiple GPU at a later date 1600 P2 or T2 1600 Watts
(I have these also - been very happy) On a Tight budget ... 1000W P2 or T2
--> is the min I would recommend for that MB setup... depends How hard your going to lean on it OC CPU & GPU --> you would Need to calculate the Load.
850W PSU May be OK ... too close for me to recommend. I believe in the Rule of thumb 100% of anticipated Load should Not Exceed 80% of PSU capacity
Save 10% from EVGA.com with anyone's Associates Code on your PSU purchase