radnaxela

The problems with your machine not booting up may vary, certain wires which may not have been placed properly which have to do with booting you pc and many more factors. Also you might want to check if your power supply might be defective, by properly placing your power supply into another pc which clearly works or have brought to a professional troubleshooter.

Depends on the game. The 6700K will win in single-threaded performance since it runs at a higher frequency and has slightly more performance per cycle. If the 5960X is overclocked it won't be far behind though. In games that utilize many CPU cores (which is a fair amount of games these days) the 5960X should win outright.

If it's solely for gaming, I would opt for a i5, though. Anyways, getting a Haswell-E (X99) based CPU would be better for (future) games, which will be supporting DirectX 12.