I'm currently expanding my mining farm and I would like to setup machines specifically for working on the SONM network. What type of machines / hardware is best for this?
Graphics Cards!! The same thing that's best for mining Ethereum & ZCash. Have you tried their TestNet yet? You can download their software and run it on your personal computer first to make sure everthing works. I would run the TestNet first before buying a bunch of graphics cards.
https://mvp.sonm.io/