You need to modify the addressing on the system to handle 8 GPUs on Linux or Windows, it won't boot out of the box that way but with some work it can be done.
Awesome, on so many levels. I only have two suggestions --
1. Put in a bay to hold a couple of server power supplies to drive the PSU's. (Which, I just spend the last hour looking at psu backplanes thinking, I could rewire that...)
2. Paint it black and up your price to about $200 grand or so. I mean, watch the video on the "Klimax 250" which I am not making up.