I actually just got the OCZ ModStream 450W. They do come in a 500 or 550W version though.
I have found this PSU to be quite good. I cant tell you how relable it is, as I have only had it for 24 hours
I can tell you that the modular setup is great. You only use the cables that you need, and stick the rest back in the box for later! It had a sturdy, quality feel to it.
My only complaint about the OCZ, is that the power cord is a bit flimsy. If I would go to reposiition my PC, the power would shut off. I replaced the OCZ power cable with my old one, and now everything is working excellently.
Overall, I would give the ModStream a rating of 8.7 out of 10!