For starters, I would change the powersupply to one of the Corsair Professional HX series.
The Corsair HX650 would be a good choice. It has a thermally controlled fan, meaning that when your computer is idle, or at low load, the powersupply fan actually turns off completely, eliminating all noise from that source.
Also, instead of air cooling, why not consider going to an All In One sealed water cooling unit? The
Corsair H80i is a great choice. It comes with 'Corsair Link', allowing you to monitor block temps and adjust fan speeds (create a fan curve, perhaps) right from Windows.
I know what I'm suggesting is a little more money than what you have spec'ed, but if you want a truly quiet machine, that's the cost!