I'm using that same switch box for my power amps as well. I don't know of anything off-the-shelf, but you can certainly design/build one. I believe the switch used on that A/B switch is a 4-pole single throw (4P1T) type of switch. If you want to switch between 4 amps, I think - but not certain - you would need a 4P4T switch which are available online. And of course, your custom box would have 8 more banana plug connectors.