I think this (http://photos.imgix.com/racking-mac-pros) is what you are after.
Their earlier article about racking mac minis is good too: http://photos.imgix.com/building-a-graphics-card-for-the-int...
Their earlier article about racking mac minis is good too: http://photos.imgix.com/building-a-graphics-card-for-the-int...
For example, you can get a Google Cloud instance with 32 vCPUs and 28.8GB of memory for around $622 a month.