Kaiser,
We have several customers running multiple SM200s on a single PC. I’m aware of one customer running 4 SM’s streaming I/Q.
You are correct in that the biggest issue is generally USB throughput, but we have found that 2 SM’s will run just fine on a single PC (higher end desktop). You only really need to consider USB adapter cards above 2 SM’s.
If you are on Windows, everything should just work out of the box. If you are on Linux, take a look at the appendix in the latest API manual. I have some notes for multi-unit use on Linux.
How much processing power you need it really going to be dependent on what type of processing you add to the system. A standard 4 core PC will run 2 SM’s if you did not perform any processing.
Regards