No. And what could this possibly add?  The Ones are already powered speakers. Just play music through the Ones.

Ethernet cables are one means for sending data packets around your system, managed by the Sonos software. They are not audio cables. This suggestion is a complete non-starter.  Sorry. 

I don’t quite understand what you mean by ‘software outdated’ - unless you mean the C:A is only capable of running on S1 and your present Sonos System is S2? 

Either way, you cannot make any use of a Sonos Ethernet port for networking purposes unless it’s connected over a SonosNet wired/wireless connection… and in any event, there’s no way through the Sonos App itself to output Sonos audio to a device that is not held in the same Sonos Household and particularly via an Ethernet connection to your old C:A.

You would likely be best to setup the C:A to run (wireless/wired) standalone on your Sonos account using the (separate) S1 App, which will happily co-exist with S2 on your compatible mobile controller device that meets the current requirements shown in this LINK

Hmm, thanks Dave. Got it. The idea was a quick workaround to not spend a bunch to use my JBL speakers. They are high-end JBLs. 

Appreciate your input! Hoped the ethernet cable might carry audio too - meaning the lack of software updates for the Gen 1 Amp wouldn’t be a problem for me in the future. Your reply has saved me from a mistake. 
 

Using a Connect *Gen 2* via S2 connected to my receiver would work (then I have to mess with my receiver).

The apprx $400 for a Connect Amp Gen 2 is probably easiest for my needs. Just $300 more then the Amp Gen 1 near me on Craigslist. Cheers

Thank you also Ken. But acknowledging my lack of sophistication in this matter, I suspect using the S1 and S2 softwares concurrently would create some hassle or conflict for me. At some point if not now.

Appreciate your reply too though! Seems I’ll just invest in newer Sonos technology and keep it all S2 (until they plan their obsolescence and we ditch all that gear and invest in “S3” etc. Hahahaha)

@GSoCalC Do you mean your Connect:amp is to far behind to be updated, because there is no lack of software updates for S1 products. They are still served with safety updates.

Using S1 and S2 can be done, but is indeed a bit of a hassle.