I recently found myself in the same situation as the OP, wanting to A/B compare 2 integrated amps with one speaker. My solution allows me to switch 2 amps remotely between 2 sets of speakers; however, only using 1 set of speakers right now. I added 4-2 source selector switch as well, but not remote controlled; Using it as 4-1 with RCA hard y-splitters to amps.. Wanted all cables to be on the same footing for a fair comparison, so purchased all new 'journeymen' quality cables from WBT.
Speaker Switch is:
Douk Audio VU3 Dual Analog VU Meter, 2-Way Amplifier/Speaker Switch
Source switch is:
I can now switch amps from listening position. I can also switch between 2 CD players and 2 phono amps, but not remotely. Works well, binding posts on amp/speaker switch are decent quality (all this stuff is made in China so...) as are RCA connectors on source switch. PM me if you'd like to a pic of setup.