Well a KME isn't great quality, and a PSU isnt something that i would skimp on, cause it could cause you to loose your whole system..
Pay up in the beginning to avoid paying 10x later.
AOpen 500w is a very very good preformer for the price, It's a forton Power Source PSU. We (SA3DOC and RRA) ran a FX57 + 7800GTX on a DFI SLI-DR with that PSU for the South African record.