@DDDDDDDDDD
In general you could use any Sonos connect if you are satisfied with the old S1 system, because the Sonos One are S1 compatible.
But I strongly recommend using the S2 system. For that you can use the Sonos Port or ad the low budget version can try to get a used Sonos connect with production date 2015 or newer. The first four number of the serial number (found at bottom of device) show month and year. Also the S2 ready version has got a play symbol on the device botton instead a mute symbol.
Ideally go with a Connect gen2 (manufactured March 2015 onwards), as that’s compatible with S1/S2 Sonos systems, which the Sonos Ones may support too, but an S1 system setup requires an S1 only product to create that type of system.
You could also use the Sonos ‘Connect’ replacement - a Sonos Port instead.
@Ken_Griffiths @Schlumpf
OK, what is the advantage of S2 over S1? The only equipment I’m connecting to is a couple of old Sonos Ones that I got for free. Some models seem to have an amp built in which seems redundant, it seems that there was a model without an amp but I’m not sure how to tell? Are the ones you’re referring to without amps?
Sonos Port seems incredibly expensive to just connect a hifi that already has everything I need into the Sonos app, or am I missing something? I have a turntable and amp and speakers so I’m just looking to replace bluetoothing into the amp for streaming with using Sonos to stream into the amp for ease of use if I want to switch rooms/speakers.
@Ken_Griffiths
The limitation already to have at least one product on S1 to downgrade a S2 device and create a S1 system doesn’t exist any longer. Don’t know exactly when this changed, but 5 month ago I created a new S1 system by downgrading a S2 Sonos One.
@DDDDDDDDDD
At the moment until 29. of February you can use a 15% off option you might have for one of your Sonos Ones as a 30% off option. It’s a limited Sonos offer for their online shop and imho a great chance to buy the Sonos Port. 
@Schlumpf A Sonos Port costs £400 which is more than the old Sonos speakers I was given are worth. The Sonos Ones are not great speakers, they’re just cheap and cheerful, doesn’t seem worth spending 400 quid to use them. If I want to listen to music properly I’ll do it on the KEFs in the main room, just thought I might be able to make use of them.
@DDDDDDDDDD
S1 is the old discontinued system. There only are bugfixes but nothing more is supported.
So the modern fully supported system to choose imho should be S2. But as a very low budget solution just to use some streaming service S1 can be ok.
The „Sonos Connect“ is the device without build in amp. So that’s the one you can use to get Sonos content to your existing amp via analogue line in or digital input.
Also you would be able to use your amp with port together with the Ones stereo pair for synchrone multiroom playback.
@Ken_Griffiths
The limitation already to have at least one product on S1 to downgrade a S2 device and create a S1 system doesn’t exist any longer. Don’t know exactly when this changed, but 5 month ago I created a new S1 system by downgrading a S2 Sonos One.
I thing you’re referring to a different scenario @Schlumpf - you can downgrade an S2 device to S1, if you have an S1 system already, but you cannot create a new S1 Sonos Household, without an S1 only product is what I was saying. I don’t think that has changed?
@Ken_Griffiths
Thats exactly what I did… creating a new S1 household by downgrading a Sonos One that was on S2. I was surprised too as Sonos support was telling me that this changed and now is possible.
@DDDDDDDDDD
Using the limited 30% offer the port would be £280. Imho a great deal compared to a used old S2 ready Sonos Connect if you take a look at the second hand prices. Really much cheaper you just can buy a used S1 Sonos Connect.
@Ken_Griffiths
Thats exactly what I did… creating a new S1 household by downgrading a Sonos One that was on S2. I was surprised too as Sonos support was telling me that this changed and now is possible.
I didn’t think this was possible either @Schlumpf
, as I’ve always seen it mentioned that an S1 only product is required to create a new setup on the local subnet, but I’ve not personally ever tested this, I’m happy to just take your word for it.
@Ken_Griffiths
For a long time it was necessary to have at least one product that already is on S1. But that also could have been a S1 and S2 compatible product like a Play1. No need of a S1 only product…
Resetting it you were able to create a new S1 household if you set it up again with S1 app. But to downgrade any other S1/S2 compatible product that was on S2 an existing S1 household was necessary.
But some time ago Sonos changed that and now you just need any product that is also S1 ready to create a new S1 household. I did it several times with a Sonos Move and Sonos One for some S1 testings. Feel free to try… it just works. 
Only Sonos OneSL is excluded… it’s still possible to use it on S1 if it still is on S1 firmware. But once updated to S2 there’s no way back to S1. That also is a thing that has changed.
@Ken_Griffiths
Would have liked to write a pm… but not possible. 
@DDDDDDDDDD
Using the limited 30% offer the port would be £280. Imho a great deal compared to a used old S2 ready Sonos Connect if you take a look at the second hand prices. Really much cheaper you just can buy a used S1 Sonos Connect.
Yeah, I got a secondhand S1 Connect on Ebay for £16 which works fine and does everything I need it to do, thanks for the suggestions, much appreciated. Downgrading the Ones to S1 was a slight faff, had to hardwire each one into the router for the downgrade process to work, but got there in the end and all working wirelessly once downgraded.
