Not sure why Sonos would find it compelling to offer a sub $50 item, instead of selling another Amp. They’re in the business of speakers/Amps, and not switches.

On the other hand, I’m not sure how a switch would affect sound degradation, or possible damage to the amp, either. There are certainly impedance matching switches out there. 

Gurnb,

A SONOS brand switch would sonically be equivalent to any good quality switch. Yes, you could argue that a switch will degrade the audio quality slightly, but this is minimal. Similarly you could argue that a piece of plate glass will degrade the image vs an open window, but the glass provides some added functionality when it rains or snows.

Two pairs of 8-Ohm speakers can be wired to AMP without using any impedance matching tricks.

Yea I agree Sonos wouldn't really be interested in making a speaker switch. I would just like to know what constitutes a good speaker switch that I can safely use with a Sonos amp. One that doesn't cost as much as the amp itself lol. Also my speakers sets are 8 ohm and 6 ohm. Ultimately it would be nice if Sonos could weigh in and make some recommendations.

Sonos never recommends third party hardware, unless they sell it here at their website.  But it's a speaker switch, there's nothing complicated about it.  If it successfully conducts electricity, it works.  Don't fall down the rabbit hole of audiophile nonsense.

Surely the phrase “audiophile speaker switch” is oxymoronic? 

So which selector/impedance matcher is recommended? I am also looking to run more than 2 pairs of speakers from a single sonos amp. 

I like the look of these particular switches, as they seem easy to use and simple to cable etc. They are available in 2/3/4-way products and can be conveniently controlled, either with an App, or Alexa. See this YT video:

https://youtu.be/2E0dYvihv_w

Here is just one article of many on the web. On a quick skim it seemed to have some good explanation.

You will have to decide for yourself whose recommendations you believe.

https://www.audioreputation.com/speaker-selectors-with-volume-control/

It would be interesting to see just how much having four speakers directly connected degrades measured sound quality. The Amp will try to compensate but trying to deal with even identical speakers presents a very different load to the Amp.

A quality impedance matching switch might well provide measurably more accurate sound.

Audible differences might not even be detectable in a fair comparison.

Lots of options, I’d think the units rated at 100 Watts or above should be good with the Amp’s 125 Watt rating.

Nice gear: https://www.crutchfield.com/shopsearch/speaker_switch.html?&pg=2

The usual Amazon selection: https://smile.amazon.com/s?k=impedance+matching+speaker+switch&crid=3GCLXKMFED90X&sprefix=impedance+matching+speaker+switch%2Caps%2C134&ref=nb_sb_noss_1

Any of the impedance matching schemes will result in some level of audio quality degradation. Sensitivity to this varies by individual. Some listeners will notice, others will not. In many respects those who don’t notice are more fortunate.

A simple switch will have the least impact, but if including the switch implies more wire, then we get into the discussion about wire length and sound quality.

Super quality impedance matching transformers for four speakers will start to approach the cost of another AMP and are very difficult to find.

Sonos has partnered with Sonance on the outdoor speakers - consider using one of their switches.  I use the SS4VC which can be had from Ebay for $60-70 and were top of the line when they were introduced.  It works great and I have it set up for two pairs of Sonance ceiling speakers inside, two sets of B&W outdoor speakers for the backyard.  The amp has no trouble powering all at once and their have been no impedance issues.