I'm running almost the same system, except I'm using 32 GB of ram, GTX 660 SC and a Vertex 4. My current OC is at 4.1 GHz, and it's been rock stable. When I first built my system, I also received Random Lockups and BSOD's. The problem turned out to be the Corsair H80i software, the software, CorairLINK is known to have problems. In my case it was in conflict with the Intel RST(e) drivers. I had to load Intel RST(e) drivers below version 184.108.40.20620 And I have had no further problems.
Oh, and by the way my temps are below 50C.