If you have a router or a switch, you can connect several net-based SDRs to one PC. And if you use SDR-Radio, which allows multiple instances of the program to run, you can operate them simultaneously. Since I have one RF Space NetSDR and one Afedri SDR-net I decided to test this. What is needed are different IP addresses for both (or all) SDRs, and different ports. I am no network geek so I had my portion of trial and error, but with the help of SdrNetSetup and disconnecting and reconnecting the Afedri I got both SDRs to play along. On the jpg below the Afedri identifies as "SDR-IP".
Both SDRs are displaying a 1250 kHz span, with little CPU load. Another interesting observation is that when the SDRs are tuned to the same frequency, their audio appear to be perfectly synchronized. There is not the slightest trace of echo or other audio artifacts. Diversity reception, anyone?