@Theo2023,

I don’t quite fully understand your post here because you start by inferring that you are looking to add the ‘Sonos Port’ to output the Denon Amp audio to all the Sonos speakers you have. Then you ask if the Sonos product can switch inputs? 

If your projector is linked to the Denon Amp over Bluetooth as a playing source, then the output will be the same as any other source that the Amp uses.

If you do connect the Ports analog/digital-out to your Denon Amp (in addition to the RCA analog-input), then you will just select that playing source on the Denon Amp using its audio input selector and you can play the audio to the speakers connected to the Amp, aswell as any Sonos rooms ‘grouped’ with the Sonos Port via the Sonos App (if required). 

Note, however, that the Sonos Port doesn’t do Bluetooth as an input method. 

Hi Ken, thanks for the info. I want to go Phone > Sonos Network > Sonos Port > Amp > Speakers, but I also want to go Projector > Bluetooth > Amp > Speakers. What I'm asking is is there any kind of functionality that allows for the amp to automatically switch between sources like HDMI-ARC or am I going to have to manually switch it each time?

As far as your DENON is concerned PORT is a cassette deck.

@Theo2023, 

The main hub at the heart of your setup is of course the Denon Amp... so the main element of switching between sources is really down to the abilities of that device, rather than the Sonos Port. I suspect it’s a manual operation. but if that Amp uses an infrared ‘remote’, you could probably add a Logitech ‘harmony hub’ or their ‘One for All’ ‘remote’, which in turn could allow switching using mobile Apps, or even voice instruction (Alexa/Google etc.), it’s a bit of a learning curve, to say the least, to set that up ... it’s just a lot easier to switch things manually, or with its own ‘remote’, if it has one?

The Sonos Port line-in from the Denon Amp can be set to trigger the audio output ‘automatically’ via the Sonos App and you can choose a default Sonos room/speaker(s) to play the line-in audio to and include any ‘grouped room(s)’ aswell. It also allows the user to set a default output volume-level for the default room. The grouped rooms retain their last-used volume level.

The line-out audio from the Sonos Port to your Amp, will mostly/likely be the built in Sonos music services, I suspect.. The volume-out level can be set to ‘fixed’ (full volume) or ‘variable’ volume .. if you use a ‘fixed volume level’ then you can control the volume on your Denon Amp, if you set the volume to ‘variable’ instead, then you can control the volume from the Sonos App on your mobile device, or if you have other Sonos products with a built-in voice assistant, you can control the ‘variable’ volume of the Port using voice instructions.

I’m not sure if that may answer all the questions you have here, but if not, then perhaps post back and either I, or maybe others here, will do our best to try to answer them.