If you have access to cheap power, free hardware and a lot of space just make one or 2 such rigs and check how they'll perform, especially now in Winter when there should be no problems with cooling.
Also note that with that Asus MOBO you can also use those smaller slots (PCI x1) and put some additional GPUs in there with the help of more risers. From the looks of it you can fit 6 cards in there.
OOOH can I use the old PCI ports too!!! NICE!!!!
Well I tried on some pools and I got an error : user already logged in when i used the exact same wallet :S Which pools did you use? maybe I could try those?=)