My understanding is that if a system contains a ‘legacy’ Sonos component of any sort, in any role, then it can only run S1 software.

‘Modern’ Connect:Amps could be used, although presumably with not so great a saving.  C:As need a wired connection to be use as surrounds, Amps do not.

There are two versions of the old Connect:Amp. The newer of the two is not legacy and will work with the upcoming S2 software.

The two versions are subtly different cosmetically: the newer version has a ‘Play/Pause’ symbol on its upper control button, the older version has a ‘Mute’ symbol.

The Connect:Amp for the surrounds will need to be run off a wired connection since it lacks the 5GHz radio required for wireless HT bonding.

Thanks for the replies. Was actually not aware of the two different versions of the Connect:AMP. Will look for a used version of the newer version. 
 

Am aware of the need for a wired connection but that is not a concern as all of my Amps will be located in the same cabinet. 

The buttons are a rough guide, but not exact.  The buttons were repurposed in late 2013, the ‘modern’ C:A dates from early 2015.  So ‘mute’ buttons definitely means legacy, but ‘play/pause’ is not an absolute guarantee of ‘modern’.

Just FYI

Did a search and there are several of the newer Connect:Amps at about 230 USD which is a lot less than the 750 USD the new AMP retails for here in Denmark. So sounds like there will be a significant save. 
 

Is there a similar “new” version of the Sonos Connect as well? Will also be needing a Sonos Port but would be fine with a used Connect if there is a “newer” version of that as well. 

Yes.

Same applies for Connect as for Connect:Amp.

Do you have any references for this? I’ve not seen a Connect:Amp or Connect with the ‘Play/Pause’ symbol that isn’t ‘modern’, but that could just be a limitation of the samples I’ve seen.

If this isn’t a reliable test, do you know what hardware ID(s) and/or serial numbers to look for?

This thread is from between April 2013 and April 2014 (first post is 6 years old) and came from a Google search item dated Oct 2013.

https://en.community.sonos.com/components-228996/i-miss-the-real-mute-button-5740728

Have to go out now, will post back later!

Thanks John, but this refers to a software change in the behaviour of the (‘Mute’) button, not to the button being physically updated on the device to a ‘Play/Pause’ logo.

I’m planning to pick up 2-3 used ‘modern’ Connects, so I want to be sure which variant I’m buying!

Confirmation from @Ryan S in the thread below that the presence of the ‘Play/Pause’ button indicates a ‘modern’ Connect or Connect:Amp.

https://en.community.sonos.com/components-228996/connect-amp-model-6826648

My recollection - which could be wrong - is that the two events pretty much coincided, i’e Sonos did not carry on making components with a mute button when the function was actually play/pause.

I personally would not rely on this alone.

@John B : The images aren’t correct.

The same is true for my three Legacy Connects; the pictures shown on the Sonos My Account page are of Modern Connects, and they don’t match my actual devices.

Yes I realised I’d been a complete plonker and deleted my comment!  Sadly not before you had seen it!

Here is part of a Sonos response concerning complaints about the change, which dates from late 2013:

“We hear you and understand where you’re coming from. We also understand that our communication on this thread hasn’t been up to standard and apologize for that. (JB comment.. plus ca change….)

The request to change the mute button to a pause button was both long-running and popular. Many people wanted a way to quickly pause (and then resume) their music without having to open and use a controller. At the same time, we understood that the mute functionality was used and loved by many, so it was moved to the volume minus, which now quickly mutes the player when held down. The PLAY:1 was the first player to feature a button labeled as a pause, and we’re progressively rolling out this change to the full product line.”

The Play:1 launched in Oct 2013.  As I said, my recollection is that it was considerably less than 18 months before the change was complete.

I’m sure you’re correctly reporting your recollection.

However, I’m satisfied that the hardware revisions which saw a change to a ‘Play/Pause’ button in the Connect and Connect:Amp were simultaneously accompanied by the internal changes which make the devices Modern-capable. @Ryan S confirms this in the thread I referenced.

Ryan S said ‘The 2015 Connect and Connect:Amp units have that Play/Pause button as well.’  That is unquestionably true.  It doesn’t mean, logically, that no pre-2015 units have the play/pause.  There was another thread in which Ryan said that he thought the internal changes and button change occurred around the same time, but he didn’t say that they were specifically linked.

But you are convinced and that’s fine. You may well be right, and my recollection mistaken.

In the same thread, Ryan S also states you could look at the serial number’s first four digits which refer to month (x.x) and year (y.y). So one should go for x.x.15 or later I guess. 

I think the evidence suggests my recollection was incorrect.  At the time, I was a Sonos reseller, and I thought I remembered only having to explain that the mute button was really a play/pause for a very short time.  But I actually located a Connect:Amp product guide from November 2014 that has a ‘mute’ symbol labelled ‘play-pause.