No need for the BOOST, wire both the Arc and the CONNECT:AMP to your router with Ethernet cables. The CONNECT:AMP does not have the 5Ghz antennas necessary to connect to the Arc to act as wireless surrounds, which is why it needs to be wired. The Sub will continue to connect to the Arc on that 5Ghz signal, no need to wire it. 

Thanks for the rapid reply!  May I daisy chain the ARC to the connect amp and then wire the connect amp to the router?  OR can I direct wire the ARC and direct wire the connect amp to an unmanaged small switch which is wired to the router? 

The den is on the main floor and only has a single CAT5E available for the connections.  I already have a netgear 5-port unmanaged switch wired from the den back to the router in the basement.  

Thanks again for all your help!

All the guidance I’ve seen suggests that both need to be wired to the router, but there’s no reason why you can’t try the daisy chain. 

Unmanaged switches are fine, it’s the managed ones that can be fiddly. 

Does the connect amp require a sonosnet somehow to bond to the Arc?  It’s confusing to me that per Sonos, if you directly connect the arc to the connect amp, you must wire another device to the router. Shouldn’t the Arc still be connected to WI-FI and the connect amp be getting its input from the Arc?   

The CONNECT:AMP pre-dates the point at which Sonos actually had soundbars, and does not have a 5Ghz antenna by which it can be bonded to the soundbar. 

All Sonos soundbars, including the Arc, use a special 5Ghz channel that the surround speakers ‘bond’ to, which is not technically SonosNet, I.e. it isn’t the same type of signal created by the BOOST.

Once Sonos released their original soundbar, the PLAYBAR, there was a substantial customer desire to be able to use the CONNECT:AMP, which had already been on the market before the PLAYBAR, as a surround driver. Sonos, in response, came up with the ‘hack’ that would allow this configuration, but only if both devices were hard wired to the router. 

The newer Amp, which does include a 5Ghz antenna,  can ‘bond’ directly to any of the Sonos soundbars, using that non-SonosNet, special 5Ghz channel.

Thanks much for the explanation. In the following Sonos article, why would you need another Sonos product wired to the router?

Wire your Connect:Amp and home theater speaker

Your home theater speaker and Connect:Amp must be wired in one of the following configurations:

• Both the Sonos home theater speaker and Connect:Amp are wired to the router with an Ethernet cable.
   
• The Sonos home theater speaker is wired to the Connect:Amp with an Ethernet cable and another Sonos product is wired to the router.

It would appear that a wired connection to some Sonos product - thereby creating a SonosNet network is needed.

In the first configuration, both the Arc and the connect:amp are wired to the router and thus creating a SonosNet network as well - correct?

The Ethernet ports on Sonos devices are only active in SonosNet mode, which requires a wired device.  That wired device could be the Arc, but does not have to be.  I would recommend not having the Connect:Amp (when used for surrounds) as the ONLY wired device.

As Bruce has said, the C:A was designed before Home Theater was even a gleam in Sonos’ eye.  Despite its lacking the fundamental requirement of a 5GHz radio, Sonos found a workaround.  It is more surprising that they troubled to make it work than that it seems a bit odd.

The Amp, which has replaced the C:A, connects wirelessly like other surround speakers.

EDIT: I assume that your C:A is already operating on an S2 setup, and so is known to be a gen 2 C:A?

thanks for all your insight.  It’s much appreciated. And Yes - the Connect amp is S2 with a 2018 manufacture date. 
 

So if I understand you correctly, for the work around to work, SonosNet has to be active in the system thereby allowing for activation of the Ethernet ports and enabling the transmission of the surround audio signal from the Arc to the connect amp. Is that correct?  
 

That is indeed correct.

It all makes sense now!  I finally understand the logic behind to two wiring configurations.

Thanks for all the explanation!

@kdc1 

It’s great you now understand the logic behind using your C:A to drive your in-wall speakers as surrounds. Just in case you didn’t know…once the in-wall speakers are set as surrounds with the C:A you will not be able to stream music to them as a separate room independent of the Arc. When steaming music to the Arc the in-wall speakers will participate. Enjoy your Sonos.