Thanks for all the comments on my GPU miner build - I've refined the design a bit, the one in the photo is my prototype one, so it has things the other ones don't. The newer ones are working really well (not that the old one was that bad, mind you) - great airflow plus it's easier to assemble now. They all are powered with the DPS-2000BB, and up until now I mod those to include two 60mm fans, but with my new design I've re-positioned it so that it's cooled by two of the 120mm fans. The position of the cards is also relative to the fans, so they get the majority of the airflow over the front and back of each card, not obstructed by the card itself. I put them on those black bakers racks:
http://amzn.to/29PTCZ3Pretty hard to beat - you can lock them together also, but the rack does a better job and I put the PDU's on the top, so it makes for a nice individual setup. The new ones also have the PSU outlet off the side, so the front and back are largely free flowing (apart from the bar that the GPU's screw into to hold them in place).
Once I'm satisfied with the overall design, I'll start a thread with a bunch of pictures for those who are interested.