How are you cooling it and what temps are the cards running at?
You can see from picture. He has "open window mod" .

I bet it is a Zelman branded window!!
Those windows rock in both functions (open or closed)!!
http://i.imgur.com/ckCu8HP.jpg?120x Sapphire R9 290
4x Asus M5A99FX PRO
4x Corsair 750w
4x Corsair 1000w
4x HDD 32Go SSD
4x 4Go
4x CPU Sempron
Misc risers
Custom wooden rig, match anyone ?

Delivering ~16.6 Mh/s
Burning ~6500W (distributed on 4 circuits of 10 amps each)
Working on a much better 19" rackable rig, cause this beast can't scale no more.
No way I'm going to put a third level on this thing

That is quite neat! Congrats!