I know that $90 + dollars sounds like alot to fork out for a PSU. However, a good PSU is the foundation of a stable dually system. If you don't get a good one, you'll have a hard time troubleshooting problems in your system. If your 12v rail isn't 28a or more (I think 33a + is the way to go) then you're asking for problems, especially if you are thinking of overclocking them. And they are great OCers. (See my sig.)
Believe me, you reward yourself in spades if you shop out a good PSU. Enermax, Antec, Forton are all good manufacturers and I've owned a PSU from each of them. I've heard some good things about the AMS Mercury too, but never owned one.
Good luck!!