Does any one have experience with a high-end amp switch or the Luxman AS-55

I have used a Luxman AS-55.  It works great although I prefer the AS-50R remote model for comparing speakers because I don't have to get up off my butt to do an A/B comparison.

Audio by Van Alstine also makes a very good comparator.  It's probably the best of the bunch but the Luxmans have worked great for me.  Good sound and no damaged gear.

The AS-55 and AS-50R can absolutely be used to switch one amp source to up to three sets of speakers or three amp sources a single set of speakers.  Just remember that it's a switch designed for speaker output only.  It's a brilliant design and is done well.  I don't think I could build myself with similar quality for what Luxman charges for these devices.

Cables?  I would just use your standard brand of speaker cables for the longer runs.  The short jumper pair to the single amp (or speaker) can be almost anything.  I prefer inexpensive silvered copper wire jumpers but use whatever you like.  If they are under 24" you could almost use coat hanger wire.  Almost...

Here's the link to the Van Alstine device: https://avahifi.com/products/abx-switch-comparator