FWIW, I've had a standard Decware Zen Switchbox for a couple of years now and find it to be completely transparent when using it to add sources to my 1-input-only "integraged" amp(s).
High quality Speaker switch box for multiple amps?
Stupid idea, I know. But if I wanted to have 2 or 3 separate amps (NOT running at same time, of course) to choose from with 1 preamp. Is there a switch box (preamp to box, box to multiple amps with a,b, c switch, box to main speakers) that is of high quality and will have very minimal effect on sound? Of course I would keep same brand/model of speaker cable at all points. Just curious