On the intel website it says the 2500k only supports up to 1333mhz of RAM, but I know for a fact that the 2500k can go higher. I read that this is because it is not "officially supported" by intel. What does this mean exactly?
The 'Memory Types' are the Intel spec Rated & Default DDR3 Frequencies; that's all it means. On either platform RAM >DDR3-1600 CAS 8 or 9 yields minimal if any 'real world' differences, and Frequencies much higher adds unnecessary instability. So for the best experience I recommend XMP Profile DDR3-1600 CAS 8 or 9 memory and in 2x4GB density kits.