I tried 2 different PSUs (the Antec Earthwatts 500W I got with my Sonata III case and a Corsair TX650 I replaced it with) but it was still squealing away horrendously, even during idle. (Tip: I made sure it was PSU by rolling up a sheet of paper into a tube, putting it in my ear and then then listening close up to the mobo, PSU and other parts.