Yup, lots of industrial options out there. Cyclone has some pretty nice ones: http://www.cyclone.com/products/expansion_backplanes/index.php Though for video cards, may or may not have a problem getting that many to work on a single system. Last time I checked (when researching price/perf FAH boxes), drivers wouldn't allow more than 8 nVidia/AMD GPUs. Though this may have changed and something Soup needs to look into before committing to a specific plan. If there is a limit, just make it easy and go 5 boxes with 4 cards a piece. They could be anything from single to quad CPU, depending on how much CPU power he wants to utilize along with the GPUs. Also, as linked above, Supermicro has some really nice multi-GPU solutions like 20 Teslas in 10U! I'm a biased Supermicro fan, as a disclosure -edit- Really check up on how many AMD GPUs you can get in a single systems. I know (and have seen) systems with 4 dual-GPU nVidia cards. Not 100% sure for AMD.