There is still a need for some good general software.
A grunty PC with lots o' memory may be needed.
I tried just two connected to the same aerial( split just bfore the USB arial connection and tuned to same FM freq.
Using SDR# I can hear a slight echo, so inherent delays in the USB to audio out path. You can run multiple SDR# instances using Zadig and using the configure drop down option near top left. You may see in the drop list a few of the same name. Just chose the next one down for each SDR# instance.
Might be awhile before I can get to this. All of my equipment is packed in boxes ready to move to new home 500km away and will need to have shed built so I can setup my radio shack again. Hopefully shed up in next 3-4 weeks. Deposit paid engaged shed erector and hired Concreter today.