People need to remember that the GPU specs for a PSU are for the GPU alone. the CPU, fans, HD's and everything else hooked up to the computer also draws from the PSU. When a PSU becomes maxed out more wattage and heat is created causing the components to wear out faster.

Another thing which I think I posted this somewhere else too is that PSU's draw from the socket its connected too. If your PSU is maxing out and drawing the full 600 watts every time then a short in the stream of power that comes out of the wall socket may not be enough. It could be shorting out and rather than delivering 600 watts to your system you could only be getting 599 which would in theory cause your system to shut down due to lack of wattage to supply it.

Also when it comes to rails on a PSU plenty of people discredit the single vs dual rail thing.

http://www.tomshardware.com/forum/18...ngle-dual-rail

As long as you have a quality PSU that provides quality efficiency you should be fine. But programs do not just shut computers down, thats 100% hardware. Program crashes on the other hand are software.