you already know this article? https://bitcointalk.org/index.php?topic=64450.0

600 USD from his source, or near double - so 1200 USD directly by trentonsystems..... i think the starting invest just for a board is to high. for 100 USD each i get a 5 - 6 GPU supporting Board. so with 500 - 600 USD i will get 25 - 36 GPUS.

Just CPU and RAM you will save a little.

I have Ordered 4 of these: https://mineshop.eu/cables/pcie-adapter-1-to-3-slots-detail

still waiting for testing if they are supported by SMOS. I have already made my Rigs with a 1700 - 2000 Watt PSU system. so it would be great if these extenders would work. Unser Windows they are already running. but still dont know about linux support.