My son's 2600k box is setup with multiple BIOS Boot profiles so he can select which set of BIOS settings he wants to load:
1. 24/7 is it 4.6 Ghz
2. Extreme Gaming is at 4.8 Ghz
3. Testing is a highly customized group of settings (HT off for example ... saves 7C) that hits 5.0 Ghz.
He's using a Thermalright Siver Arrow Air cooler. These were our (1st day OC Settings) and Core Temps .... little tweaking dropped them some and also TIM cured so that we were at 75C at 4.8
Stock 51,53, 53, 51 (1.224) LLC = Auto
4.0 Ghz 52, 54, 55, 52 (1.016-1.024) LLC = Auto
4.2 GHz 54, 56, 57, 55 (1.256 - 1.264) LLC = Auto
4.4 Ghz 56, 60, 60, 67 (1.280 - 1.288) LLC = Auto
4.6 Ghz 62, 66, 68, 65 (1.360 - 1.368) LLC = High
4.8 Ghz 71, 77, 79, 72 (1.408 - 1.416) LLC = Ultra High*