I noticed that you own a H77 board.
According to Intel
, " Intel H77 Express Chipset also enables overclocking features of unlocked 3rd generation Intel® Core™ processors."
So, I'm not sure if you can overclock your i5 2500k with it. IDK, maybe you can get a moderate overclock with the H77 board, for which a Hyper 212 Evo would be a good choice.http://www.newegg.com/Product/Product.aspx?Item=N82E16835103099