the psu is all about quality, and Amps
for the rosewill one which isnt a very good brand
+3.3V@30A, +5V@28A, +12V1@14A, +12V2@15A, -12V@1A, +5VSB@2.5A
for teh forton one
+3.3V@22A, +5V@21A, +12V1@18A, +12V2@16A, -12V@0.3A, +5VSB@2A
the main Amps yo0u are looking for are +12V +5V and +3.3V you want the 12V over 30A i believe, and if there are dual +12V you add them together.
there is a psu section in the guide at the top saying what you need when looking for anew computer title
AIM/Xfire - pzerofgh