@Turibio,
The fact you have no power supply at the rear of the Sofa, limits your options here - so I would just stick with the Beam/Sub Mini for the TV audio. For the TT I would personally add two Era 300s and place those out in front either side of the TV and if you find you still need more bass than they are able to produce, with adjusted EQ settings, then you can always consider grouping those speakers with the Beam and Sub-Mini, or even add another Sub.

The reason I suggest the Era 300s too are if you can find a way to get power to the rear of the Sofa, you can always go onto to move them behind your seated position and set them up as HT surrounds instead.

I would also consider perhaps getting a stereo pair of Era 100s for use in the Kitchen/Dining area aswell - again these can be grouped with the other Sonos rooms for music, but nice to have the music audio in that area too.

Another thing I would not rule out here, is the Sonos Amp and two in-ceiling speakers, but that’s not something I personally prefer, but it is an option to perhaps consider as they could maybe used as both TV surrounds and for music in the Dining area and maybe solve the issue with power cables behind the Sofa. I just don’t like ceiling speakers for TV surround audio, but that’s something for you to decide.

Thanks for your reply Ken, I have a further questions to address you.

-If I group a pair of ERA on their own, can I use them when playing TV as well?

-When Grouping Beam, Sub and 2 ERA together, the ERA must be configured as surround only or can be also configured as front speakers? 

-In case I use the speakers for the turntable and music streaming should I still consider the ERA300 only or maybe think about the Five. The price difference isn’t so much.

PS. I will also consider the tip to get additional speakers for other rooms, the main room where I have TT and TV it is only 20 square meters.

If you group other speakers with the TV you’ll hear them at a 75 ms delay. Not a problem in different rooms but too close together and it can be aggravating.

You can’t Group individual Sonos speakers as such. Each Sonos or set of Sonos (stereo pair, Theater) has to be set as a Room, then you can group rooms. 

If you have speakers added to a surround system as surrounds they have to be removed from the surround setup to be used individually.

I’m a big fan of the Fives for stereo music listening but from listening to other folks here the 300s aren’t bad and will do Atmos if your source supports it.

As to power behind the couch, there are several options that might allow you to run a power outlet out there, then use the 300s as surrounds.

https://www.amazon.com/s?k=under+carpet+power+extension&crid=2D4JJTIKPLFJO&sprefix=under+carpet+power+extension%2Caps%2C175&ref=nb_sb_noss_2

Hello Stanley and thanks for your reply,

so following what Ken and you wrote, your recommendation is to keep the HT as it is (Beam Gen2 + Sub mini), and to add a pair of speakers (either 300 or Five) plug to the  turntable. Future add-ons might be Sonos one or Era 100 to be added in the main room or other rooms to enhance sound field of music setup. 
Correct?

Sonos do say the Fives are best for stereo music, I believe, so them over Eras would be my recommendation. If you are the principal music listener, another layout might be to put the speakers on the wall opposite the turntable, and use the single seat on the sofa as your listening position. You have power for the speakers over there already.

Hello again, I’m still thinking about my main room for music/TV layout. Actually I have Beam Gen2 and Sub mini.

I’m now more focused to complete the HT with a pair or Era100 rather than buy a pair of Five for Music only, which I hope it will comes in future.

Since I cannot place speakers behind my sofa, I’m struggling with positioning and pairing options.

Would be better to group the 100 together with Beam and Sub, even if they won’t be positioned in correct Dolby orientation. This will allow best Trueplay and to use 100 also for TV.
What if I cannot place one of the 100 exactly behind my sofa?

Or maybe would be best to pair the 100s as stereo and group them with HT for music only? With this option I can place them where I like in the same room as HT. In this case should I run Trueplay for each setup, and will the sub manage bass also for the 100?

Thanks in advance, Gianluca

To clarify some terminology first: in Sonos-speak, you bond your surrounds to the Beam in a home theatre system. In a multi-room system, you group rooms to play music in sync across multiple rooms. The Sub is also bonded to a speaker/speaker set in a specific room. 

If, as you say in your latest post, home theatre is your focus, then the speakers need to be in the “proper” location, because the 5 channels of sound are designated to specific speakers/speaker positions. Indeed, Sonos will expect/require you to allocate two speakers for surround duties, not just one. To see a visual of an aircraft flying overhead but to have the sound of it, as it flies away, coming all from one side, or from in front of you, rather than from behind totally screws your home theatre experience.
 

As already said, unless you can run power to behind the sofa, stick with Beam-and-Sub for movies. 
 

As far as music is concerned, try the Eras alone, then group them with the Beam, and decide which resultant sound you prefer. 
 

Your Sub can only be bonded to one room, but you can break the bond and allocate it to a different one. 

Nik,

thanks for your reply.

one further question, If I group the pair of eras and the beam+sub, will the sub crossover with era also as he do Wien tre Beam?

No.

In terms of crossover setting, if the Sub is bonded to the Beam, it (sonically) plays with that alone, even if you’ve grouped in other rooms. If you de-bond it from the Beam and instead bond it to the Eras then it works with them but won’t take account of the Beam, even if the Beam is then grouped with the Era “room”.

Normally speakers are in different physical rooms rather than in the same physical space - hence the identifier labels that Sonos uses are referred to as rooms. (You could call your rooms Tom and Jerry: they are just labels, though most folk will easily remember which is Lounge or Bedroom if they’re the roomnames they’re using.)

It would be quite an effort to try to establish how Sub should play if it had to calculate crossover frequency for up to 30 speakers and combinations of all the speakers Sonos currently supports. And totally pointless, since you’d probably not hear the Sub from a different room than where the Sub was located in a 30-device home!