I was recently told this ' Intel Core i7-2600K you want to stay with the 1.5v ± 5% otherwise it can damage your processor and void your warranty. ' Therefore I wanted to use G-Skill 8GBXL Ripjaws X which is at 1600Mhz and after a small amount of time reading I find out that SandyBridge only supports 1333MHz?!
I'm also worried that the G-Skill 8GBXL Ripjaws X won't fit under my NH D14. So can anyone recommend me RAM which is 100% works but does not have massive heatsink fins or that you know fits under a NH D14
Sandy Bridge at stock memory speeds supports up to 1333MHz. The memory can be overclocked far above that. I do recommend you don't go over 1.5v with the memory (you can go lower if your modules support it). Overclocking always voids your warranty... If you bought a k edition CPU then your warranty should be the least of your worries.
I don't know how much clearance the NH D1`4 needs for the RAM slots so I can't make a recommendation there but anything that isn't huge should be okay.