Wow, why are these so expensive? ;O
Yes, you need to buy a fan/liquid cooling system for your CPU for OC. If you're doing small OC, fan cooler should do but if you are planning to do some heavy OC, liquid cooler is needed. This build is overall solid, I wouldn't say it's really future proof but it will last you few years of new games with medium settings. Just upgrade your GPU down the road like the 780 or if something better comes out.