"1000w KingWing" - also be a little concerned about any PSU that makes me think of parts of a chicken. and/or hungry .
The best Power Supply that I have found is the XFX ProSeries 1050W
http://www.newegg.com/Product/Product.aspx?Item=N82E16817207021
Currently running 3x 7950s and have overhead for 1 more atleast.
$190 and its fully modular, I'm very impressed by this power supply.
I'm using XFX Power supply and XFX video cards. 5 year warranty on the power supply and lifetime on the cards. I don't know how the other brands compete.
Are you overclocking your cards? With my KingWing lazer platinum 1000w I was reading a little over 1000w from the wall when I would start overclocking a bit, that is with 3 7950s. What are your cards? How do you measure that you would have room for a 4th one?
Thank you
P.S: I am looking to buy a PC Power & Cooling 1200w Silencer MK 3 platinum for 4 7950s. I returned the KingWing.