Nevrsadie: Did you have your case open when you ran it at low voltage. The reason I ask is because your minimum temperatures are showing up as 30, 30, 27, 30 in your screen shot with TJMax set to 100, 100, 105, 105. The 30C numbers in a 22.5C room seems about right to me. I'd use my TJMax values and then you'd only have to bump up core 2 a little bit with some idle calibration correction.

My Quad is similar that when I run Prime95 for a few minutes, there is still a difference in temps. Not as big a difference as what you're seeing. As I run Prime95 small FFTs longer, core 2 and core 3 start to catch up. It will forever be a mystery what is really going on here. I'll go run some Prime and post a screen shot or two so you'll have something to compare to.