Not really enough detail to give an intelligent answer, in general, I’d connect the CD player to the Amp using the CD jacks, and the Port to the Amp as well, using a tape loop/connection. But it all depends on the Yamaha, and what connections it has on it.

In all honesty, I’d forego the Yamaha altogether, not sure what value it is providing, and plug the CD player directly into the Sonos Port.

Well, actually, I’d rip all the CDs to a hard drive, and use the Sonos to play the library from there. No need to keep the Yamaha or Rotel…although the Rotel might be slightly useful in the future for ripping, depending on the computer situation. 

I don’t know which YAMAHA you are using and other system details. Consider connecting PORT as if it is a cassette deck.

Thanks gents for the good advice. I may have to tackle this problem in a very different way. 

I ripped my CD collection, found I never used either the CD player or the CD changer and gave them away to get shelf space back. The AVR system soon followed.

Keep the Port around so you have it if you buy a non-Sonos compatible turntable and want to stream from it.