Amplifier and Speaker A/B switcher

what about just a speaker switcher to switch one pair of speakers between two amps? would that avoid some degradation?

Depending on the concerning ear, everything you put into the signal path will degrade the sound.

Years ago, I needed to do what you want.   But I needed to be able to switch 4 turntables, 6 amps/receivers, 2 aux and 12 pairs of speakers. Plus, spares of each.  I had a hard time finding the switches i needed.   And wiring them together would be a rats nest pain.  That's why you pay the big bucks. 

So, I made a Patch Board.  Pamona banana jacks for power outs and speakers.  RCAs for turntable, aux, pre out and amp in.  Using patch cords I could switch. ab, mix every which way.  Was not a quick turn or push of a switch but did the job.  And all the connections were right in front of me.

i think i'm just going to swap the speaker cables by hand between the two amps for now. hopefully the banana plugs can handle it daily. i don't want to lose any sound quality.

still open to any great ideas or good devices for this

"swapping the speaker cables by hand" That's the way most of us do it.

What about turning the amps around so the speaker connection are facing outward?

How often do will you be doing this?

If I had to do it again, I.would still go with a box, a bunch of dual banana jacks and a pair of dual banana jumper cables.  I don't think there is a switch that is as neutral transparent as a banana plug or screw down connection.  High current solid state switch?  Works for line level switching.  I'll throw this one at McGowen.