I bought a 500W Q-Tec PSU last year to run quite a low spec system (Athlon2800XP, GeForce6800, 1 optical drive, 1 HDD) and it wouldn't even POST. I replaced it with an old 350W PSU I had laying around and it was fine.
I think Q-Tec quote 500W when its really 2 x 250W on different rails (as I...