Power is what runs everything in your computer as you know. The main technical difference is the shaping of the wave, which affects computer stability for the main part.
-Cheap PSU's are rated different, in non real world conditions
-Cheap PSU's highly exagerate their power, even at 50 celcius.
-Cheap PSU's do not contain the power in the right places.
A cheap power supply can frequently cause to computer instability (Power supply's are one of the largest problem causers in modern computers) and, can even fry an entire computer.
Now I have lost a computer to a cheap power supply, and have had another cheap power supply burn.
It's your descision, cheap, medium line (recomended) or high end.