lol 1.6 PSU what you on mate, I have built more custom pcs then i had hot dinners, my own runs a i7(1366) at 4.3GHZ HT on, 8TB 4x2GB HDD 1 SDD & ATI 6970. Asus Xonar Essence Thats on 750w. Do not skimp on the psu i would rather have a 750W top brand then a 1400w non branded rubbish
You could always mod the case and add a second dedicated PSU for the Hardrives / Optical drives - Then run the GFX cards and MOB off the original, that would give you 3200watts; unless you also want a mainframe and server that should suffice!!
Seriously, I have a decent setup with i7, multiple 1tb drives etc and run with a Corasir 850w.
I've run 'Mother of all Graphics Cards' and quad-cores on 400W or less. A 1600W power supply is going to set you back over £200, and it's a massive waste of money unless you're running FOUR high-end graphics cards with dual processors and 24GB+ RAM. Basically, you don't need one. You probably want about 600W or less.