Correct, there are not an n number of inputs on either an Amp or Port. The Amp is designed to drive Sonos content for third party speakers, not replace a multi input amplifier. The Port is designed to bring the Sonos content to an already existing amplifier and speakers, and accept any content that might be connected to the amplifier.

Airgetlam is correct. However, through Internet Radio, you can likely get all stations you might be looking for, and you could digitize your CDs, storing them locally on a computer or network attached drive, and have them available to play at any time on your Sonos device. Then, you could just have the one input from record deck going into your Sonos device’s line-in connection. Then you would be controlling what’s playing using the Sonos app on your mobile device and be able to access just about anything you’re looking for without having to change inputs.

Plus Sonos isn't designed for physical media.  Time to rip those CDs and sell the  CD player!

Ryan beat me to it.

As stated, the only input needed is the turntable.  It's just so much easier to replace the others with the digital equivalent, plus you get the benefit of track info, playlist creation, search facility, etc.

If all you want to do is bring internet music access to this set up, adding an Echo Dot will do this very cheaply. If you spend a little more on an Echo Show 5, you will also get album art display for all such music that you play via the Show. You can even play YouTube music videos then, with sound from the existing system.

On the other hand, if you want to add music from this set up to more rooms in the home, the Port may suit as an additional source as well as a means to expand - does your amplifier have tape out/audio line out jacks?

Thanks for all the replies. Following up on these I am now thinking of digitising my cd collection but I don't know how to do that, I have a Mac mini with nothing into which I can insert a cd.

One reply I did want to respond on:

Kumar. You wrote “On the other hand, if you want to add music from this set up to more rooms in the home, the Port may suit as an additional source as well as a means to expand - does your amplifier have tape out/audio line out jacks?”

My amp does have one pair of tape out jacks. Why is that significant ? 

Then you can wire these to the input jacks on the Port and wire the Port output back to a unused input pair on the amp, which in all likelihood it has. 

You can then have the Port play whatever the amp is playing from any of TT/CDP/Radio, to other Sonos speakers in other rooms. There will be a small lag, but for speakers that are not in the same listening space as your speakers today, it won't matter. 

And you can also play internet music from the Port via the integrated amp and from other Sonos speakers when you add these; in this case, all in perfect sync. For this, set the input setting on the amp to the same input pair to which the Port is wired.

I am not sure what connections the mac mini has, but I should have thought it would be possible to connect an external CD/DVD drive.

You can rip with one of a whole host of ripping programs. I have been very happy wirh dbpoweramp. Rip to lossless FLAC, unless you are a dedicated Apple fan, in which case you might use ALAC. 

Are there not service providers that do this by now? A business opportunity, I think.

There are certainly firms that will rip your CD collection and return the CDs and a flash drive or other storage medium with the ripped files on it.

@John B : That’s got the OP sorted then

To rip your CDs, just get one of these:

External DVD Drive, USB 3.0 Portable CD/DVD+/-RW Drive

Thanks again for the replies. I think I now need a detailed chat with a Sonos expert in the shops to see where it can take me.