The Milk Crate route with a tiny twist.. just set the cards at a 45 degree angle to help cooling and put a 15$ box fan on the top. Cards stay about 75 C or less.
Also powered with two 750w PS as that is cheaper than one 1200w PS.. using the add2psu.com module.
Also this draws ~1200 watts at the wall, and does ~2.4Mh/s. I can probably improve this some, just have not had the time.
That is a cool looking rig, but aren't you kind of adding 2 points of failure?