If you want the bookshelves to be the main speakers, connect the TV to the Amp’s HDMI ARC port. Connect the subwoofer to the Amp’s sub output. Then set up the Beam as a separate room. When you want to play the same audio to the bookshelves and Beam, group both rooms together in the Sonos app.

NOTE: You will probably experience a slight audio delay from the Beam when playing TV audio. Streaming music will be in sync though.

Thanks Guitar! Is there any way to avoid the delay when playing TV audio? I could imagine that might be a bit disconcerting

For your needs, IMO, you should have two Amps. That is the only way you can use a third party subwoofer and synch the sound for TV and music. You would also need another pair of passive speakers.

The Beam cannot be the "slave", it has to be the "master". That won't give you what you want. 

An alternative to the second Amp and passive speakers would be two One SLs 

No, you can’t avoid it. Some users have reported they don’t notice the delay, but I’ve tested it on my own Sonos system and the delay is VERY noticeable.

Bummer - we used to have a Sonos Playbar with a couple Sonos 1’s and that played all three fine together as a single room, is the issue that we’re using the Amp? Or have they changed their setup?

The Playbar and two Ones could only work as one room if the Ones were added as surrounds. This is still the case. Absolutely nothing has changed.

Please see my earlier post.  The Beam is the wrong product for your needs IMO

As far as I know, the delay has always existed no matter which Sonos device is grouped with the Sonos home theater product when playing TV audio.

Were the Play:1s set up as surrounds with the Playbar or where they just grouped together?

Thanks John! So is the 'issue' (so to speak) with the Amp, the Beam, or the combination of the two? For example, could we have an Amp and a Sonos One as a single room, just not an Amp and a Beam? Thanks! 

The issue for you is that the Beam must be used for the front channels. That forces you to use the Amp for rear surrounds. That is fine in itself but you said that wasn't what you wanted. 

Also, in this configuration you cannot use your non-Sonos subwoofer. 

And the Beam is better for TV than music so that doesn’t fit well with your priorities.

You can set up the Amp and two Ones as a single surround sound room. When the Amp is used for the front channels like this you can use your subwoofer. Your bookshelf speakers are in front of you, which is better for music. (You can choose to have the Ones virtually silent or in full volume stereo for music.)

In summary, there is nothing wrong with a Beam + Amp setup in itself. It just doesn't give you what you are looking for IMO.

I hope that is helpful .

https://support.sonos.com/en-gb/article/set-up-your-sonos-amp

From your profile it looks liker you have  the speakers needed to try this out, unless you only have one Sonos One.

As you describe the room as 'huge' you might even need Flives for the surrounds. That is unlikely but you can see how it goes. 

This topic made me start thinking about my own setup. I have the Amp for TV-audio, connected du sub & two One as surrounds. I would like to have a Beam as a center channel for TV. I know this is not possible, but would it work to use a HDMI-splitter and connect both the Amp and the Beam to the TV? That way they should play i sync, but maybe the audio would sound weird?

@EMIA . You could not use an HDMI splitter because the signal is HDMI-ARC. I don't know if an HDMI-ARC splitter exists and I don't propose to look, as I do think this is likely to sound weird!

Thanks John! This is starting to make sense!

Now I see where my misunderstanding was: I had imagined that Sonos was effectively ‘getting away’ from the tradition 5.1 (or 4.1 in Sonos’s case) model, and instead letting you position any speakers anywhere with their auto-balancing algorithm. It sounds like they are sort of doing that, giving you more flexibility in positioning, but you still can’t have 3-4 front speakers (which is essentially what we were going for with a Beam+Amp combo).

To be frank, that doesn't bear much resemblance to reality. I don't see any evidence of Sonos "moving away from traditional 5.1". How and why would they do that when the content still comes in 5.1 formats?

I don't really understand your comment "or 4.1 in the case of Sonos". Could you explain that one please?

Yeah it was just my imagination based on our usage of their TruePlay app; I was imagining there was more going on there than there ways.

And indeed there’s no benefit to move away from 5.1 for surround sound, as that is the format the audio comes in; rather I was curious about the potential for innovation in how Stereo is delivered, the potential for delivering a stereo stream through more than 2 speakers. You *can* in theory do that today through ‘traditional’ receivers just by outputting the stereo signal to multiple speakers, but without any intelligent sort of balancing it won’t sound good (unless you make extremely painstaking efforts in your speaker matching, speaker placement, and room audio design). My imagination was that Sonos had solved that problem using their app-based auto-balancing, allowing you to play multiple speakers in stereo without as much conflict. Obviously that’s not the case, was just a concept that interested me.

By 4.1 I’m referring to their ‘virtual center’ approach. For surround sound you can set it up with Left, Right, Rear, and Sub.

OK I'd agree with most of that, given that you have realised that things are not as you once thought they were.

I am not an expert on Trueplay  but I suspect that "auto balancing" is not what it is about at all. It is done only on a room by room basis (Sonos room, that is). It is more to do with room acoustics than "auto balancing".

The "virtual centre" does not apply to soundbar based Sonos HT systems. It only applies where an Amp is used for front speakers and effectively gives 5.1.