A quick overheating fix is to take the side panel off your case and stick a ~10" house fan blowing into your case while stress testing. Although your posted temps look pretty normal.
All heatsinks are free of dust and all fans are working?
Try re-seating the little chipset heatsinks on your mobo.....worth a shot (very little TIM required)
How long did you run MemTest? Overnight?
You might want to try performing a backup and doing a clean OS install. At least that "should" eliminate any software related issues.
Main: i5-3570K, ASRock Z77 Pro4-M, Asus GTX660 TOP, 500GB Crucial BX100, 2 TB Samsung EcoGreen F4, 16GB 1600MHz G.Skill @1.25V, Silverstone PS07B
HTPC: A8-5600K, MSI FM2-A75IA-E53, 4TB Seagate SSHD, 8GB 1866MHz G.Skill, Hand-Built Wood Case