14nm skylake runs cool.
You will run out of safe vcore limits before you run out of thermal limits.
Your case is a decent cooler.
A simple cryorig H7 will do the job.
Even with a 120mm fan, it is only 145mm tall.
As of 5/2016
What percent can get an overclock at a somewhat sane 1.40v Vcore.
I7-6700K
4.9 2%
4.8 17%
4.7 59%
4.6 93%
4.5 100%