How do you A/B amps in your system?

@peterf6 My entire system wouldn’t be an option in many living rooms....I currently have 4 sets of floorstanding speakers in my living room. My amp is 7 ft wide and 300 lbs.

I also find that I have to reposition my speakers when changing amps, so another wrinkle, at least for me. But my comparisons are long term, not A/B. 

Yes - quite simply I reconnect the sets of cables (input ICs & out SCs) between 2 amps. Move the amps themselves, if space requires. You swap in an amp, and then listen AS NORMAL to your preferred music material, for a duration. Rinse, repeat. For an experienced audiophile, the sonic differences (more importantly - your interpretation of them) will at first manifest, then solidify / stabilize, and finally become quite consistent over time.

Switchboxes meant to reduce swap-time is a false optimization. Such scenarios do 2 things:

1. They fatigue or outright shut-off the portion of our brain that derives pleasure from music listening. This part is crucial to our subjective interpretation and overall listening experience. 
2. Fast AB comparisons further engage the brain's logical center, with powerful pattern matching that says: "yep that sounds similar enough; it's the SAME". That's why fast-switch AB or ABX tests often find little to no difference.

Passive two-way speaker + amp switch. One click and A/B. Works great. Luxman makes a high end version.