expensive? but if you need it!

The problem you have two amplifiers and a pair of speakers, now the choice is not great. It is important to be cleanly separated and the transitions of the circuit are properly executed. This is the AMP-S by a rotary switch implemented the three positions has AMP1, 0, AMP2, here I find the intermediate position 0 very good, that there is a certain increase in security during switching.

The AMP-S is a very simple construction, behind the ordinary connectors are going from there cable forward to the rotary switch, that was it. The cabinet is heavy, so that the cables have their fixed point. The case is screwed and I'd want to bet that's true craftsmanship, because the AMP-S is not a mass market level, so the price (again, I suspect that the rotary switch is very good).
For connection, one has to approx 13.5 cm * 6.0 cm 12 connectors, as there is not much space, but if you have not too thick cable, you should do it well, to fix them without banana plugs. The AVRs can go closer and cheaper.

The AMP-S is made in China and the importer is selling Sintron in Iffezheim.

I tried the check to measure the resistance and as already thought is not measurable with my instrument.