If you want switching between amps with MIDI control, there are Lehle amp switchers that are programmable (i.e., you can choose to have only one amp on at a time, or set them up for two or more amps on at a time) and they respond to MIDI.
The blue pedal on my board below is the Lehle 1 at 3 amp switcher, and it works as advertised, absolutely does not suck tone, etc. I don't use MIDI on my pedalboard, I just use the buttons, but it does respond to MIDI messages when it's set up to do that (the thing is awesomely flexible).
When switching between 3 amps, it automatically lifts the ground on any amps that aren't on. So there are no ground loops, like you get with most ABY boxes.
If you want to run two amps at once (I don't do this very often), you do need to use a passive ground isolation box on each
additional amp that you want to run at the same time (i.e., one amp must always have the signal grounded).
Lehle makes one -- it's a useful thing to have around, and I have it in the gear cabinet for those times when I want to run two amps, or need to isolate grounds on other gear.
The 1 at 3 also does some other tricks that I can't remember, simply because I don't need those tricks and was too lazy to learn all of its capabilities.