There are plenty of other M-itx cases out there.
Yes the 4690k is good for overclocking, but that won't help gaming performance. Overclocking High end CPUs only matters when the GPU is not a factor. Generally with two gtx770s or a single 780ti, is when you see a CPU Overclock start to make ANY difference at all. And even then we are talking a few FPS.
Modern day overclocking is a hobby, not really for big gains on high end CPUs.
Also, there are $50 air coolers that will blow that liquid cooler away in performance and be WAY less loud.