I’d like to set up three separate systems going into a switch box that all go out to the same pairs of speakers. I already have a two in/one out box and I’m having trouble finding something that offers just one more input. The idea is that I would have three separate systems built around my 9090 DB, STA-2100 and SX-1010. The speakers at the other end are stacked Advents.
You could take two 2-in 1-out boxes. Two amps into the first box, the out from that into the second box, and the third amp into the second input of the second box