Connections for amp + arc + ceiling + sub

Further note. The Amp doesn't need to be by the TV and it may be more convenient for it to be elsewhere. However, keep it in the same room. The elements in  Sonos HT systems are designed to communicate with each other directly using their 5GHz radios. 

Excellent, thank you, John! It’s very nice to get such a quick response.

My original design is to have ethernet connected from the router to the Amp, for clean, fast data. Would there be a benefit in connecting ethernet between the Amp and the Arc, even though it’s not necessary? The reason I ask is that, as a “wire guy” I feel more secure with the closed system that cabling provides (less EMI, and so on). Nevertheless, I’m fine with wireless transmission.

As you put it, “the Arc is running the show”. I guess the only functions of the Amp would be powering the ceiling speakers, and the portal for user interface only? Sounds like the Arc and Sonos sub have their own internal amplifier. Is that true?

Hi. I understand the desire to wire, but I would suggest keeping the Amp wireless when it is being used for surrounds, as it's the way Sonos HT is designed to work.

It would be fine to connect the Arc to the router by Ethernet, for playing music sources. 

Sonos speakers are active (powered) speakers, and it is fundamental to the system that the Arc and Sub are amplified. I think the Arc contains 11 amplifier-speaker units, but I'm sure you could check that on the Arc's product details on the Sonos site 

Just wanted to add that the amp is not the ‘portal for user interface’.  The Sonos app can connect to any and every Sonos speaker/device/room.  When connecting to Sonos through 3rd party apps and services, such as Amazon Alexa, Google, Spotify, etc, the connection is made to individual Sonos rooms.  The amp doesn’t play any special role in this regard.

Indeed. And when the Amp is used to drive surrounds it doesn't even appear as a room in the Sonos app.  It just plays what the Arc sends to it.

Okay, I’m learning.

He’s also got speakers on his patio, and in his garage (two in each location). He plans to get at least one more Sonos Amp, likely two, to power those. The patio speakers are Sonos (I think by Sonance?), but the ones in the garage are Bose. Since the Amp isn’t used as an interface, and the Bose have no wireless capability, I guess I have to connect an external source to the analog inputs to the amp, yeah?

Likely a Sonos Port would be the ideal device to get the Sonos output to the analog input in those BOSE devices. 
 

I am somewhat persnickety about things, but Sonance is the maker of speakers, Sonos has a marketing agreement with them, so they’re technically not Sonos speakers per se….but since you’re driving them with a Sonos Amp, it probably doesn’t make any difference. 

Are the BOSE speakers passive or active? Active speakers typically require a line level analog input. Active BOSE speakers may require some sort of control input from a BOSE system. Finally, some BOSE passive speakers assume that there is a specific BOSE equalizer in the system and it is not possible to use an external equalizer with AMP.

I am afraid I don't know what you mean by "the Amp isn't used as an interface" but the conclusion that you need to use the analog input on the Amp is incorrect.