I've had my rig for just over a year. Two weeks ago I started playing Saboteur, which crashed on me on a daily basis, forcing me to hard reboot, but I kept doing it coz the game is so fun.
Gradually, instead of just freezing up, I would get a "no signal" on my screen. After this started happening, I stopped playing the game.
From there on, things just got worse. The next stage was that I would get the "no signal" on other programmes...and even just after Windows finished loading. Even hard reboot didn't work after that--I had to switch of the PSU before I could boot.
Now, my motherboard won't post. The fans come on and so do the motherboard lights, but that's about it.
The Corsair 750 is an excellent PSU and should have no issues running your system.
A clogged HS and overheating CPU defiantly could cause your issues.
Take a can of compressed air and clean out your entire case.
Afterwards, please use Coretemp or Realtemp to post your idle and load temps.
Also, are you using the stock cooler and did you make sure it is properly seated?
Stock Intel coolers can be a major PITA to get seated some times...