Most people swear by this one:
http://www.dhgate.com/product/dc-12v...141191611.html

It has a bed of screw terminals across the back, so you don't have to crack the case and rewire it.

The PC power supply is an ok idea, but unless you get a modular supply, you will have a lot of extra wires to manage. Having said that, if you have extra items that need power (extra extruders, bigger heat bed, print-area lighting), then a PC supply would be nice, because if you upgrade it, you just unplug the old and plug in the new.

It's kind of a justgement call, based on personal preference.