As above, I have the Supernova 750G+, I bought it this year and it says whisper-silent, but really it's aircraft startup :-)
Its the only thing that makes a sound in my rig, it basically runs at full power and chunks air like no tomorrow.
I regret purchasing it, to be honest, but too late to return or exchange.
Just being able to slow the fan would really help. If not, I guess ill have to eBay it and get a Corsair PSU I know off that allows for fan control.
Cheers,
Ben