I am not going to OC it. In fact, I chose the 'K' version just in case I want in the future. Should I use the stock cooler (for stock speed) or get a CM Hyper 212 EVO?
you can stick to the stock cooler until you overclock. in your case the cm evo would just help reduce noise. the stock cooler will keep temperatures at normal levels on a K cpu that's not overclocked. that's what it's designed for.