To close the loop on this, I took advantage of a Black Friday sale at Sweetwater and did go with the
CONTROL2USB monitor controller.
Having used it now for about a month, it is exactly what I was looking for. I have my amp modeler going into one of the stereo the inputs, and my drum kit is run into the 2nd. The 3rd is "empty" as that is shared by the USB interface from the computer, so I'm dedicating that input for that purpose. The 4th input is currently unused. Going out I have one going to the mini amp connected to bookshelf monitor speakers, one going to the FRFR powered speaker, and one to a Bluetooth transmitter which gets the signal to the stereo system in the living room, so I can run my music management software on my laptop out to the stereo.
The other day my BIL was over and we were noodling around, working out an Allman Brothers tune, with him on keys. I used the "Studio out" connection for his headphones so the rest of the folks in the house didn't have to put up with our experimentation!
The only feature I'm not using is the "talkback". Since we were sitting about 6 feet apart, it seemed hardly to be needed!