The problem lies with the fact that there is no way to connect the Sonos Ones to your TV. That requires one of the Sonos sound bars, or a Sonos Amp with third party speakers. 

I like the concept of having separate speakers for music and TV, though. Probably because I have such a setup, with a pair of PLAY:5s which I use for music flanking the PLAYBAR I use for TV.

Oh, one more thing, which isn’t clear from your question, but should probably be mentioned. All Sonos sound bars, the Beam, PLAYBASE, and PLAYBAR have all three front channels in the single enclosure. You can’t use the soundbar as a center channel, and have separate speakers as front left and front right.

However, the Sonos Amp does allow you to have separate front left and front right third party speakers, but creates a phantom/virtual center speaker by combining the left and right speaker channels. 

Sonos has no setup currently that allows the use of three separate speakers up front in a Home Theater.

Many thanks for your thoughts Airgetlam :-)

After almost placing the order but then reading a few more reviews, I'm now at the point where I'm considering taking the Beam instead of the Sub.

Reasons for this 180 are that from what I've been reading (I'm no audiophile nor expert) Subwoofers are really quite inappropriate when you're in an apartment that shares walls, floors and ceilings with neighbors )which happens to be my situation) and that the Sonos Sub is “overkill” for probably 90% of users anyway.

Together with some other articles this brings me to the following (new) questions:

1. My understanding is that the Beam does add some “Sub” experience, is that correct?
2. Not considering form and size, the Beam is superior to a Sonos One speaker, correct? (i.e. sound-wise the Beam can do anything a Sonos One speaker does, and more)
3. When playing just some music, can that music be played through the Beam and 2 Sonos One speakers simultaneously?

If those points are all correct, then my current consideration is to just get 1 Beam for in the living room (below the TV) and 2 Sonos One speakers: 1 for in the kitchen and 1 for in the bathroom. If that setup can provide a good music experience in the living room too I'll be very happy and my neighbors probably too.

Thanks again in advance for your thoughts!

Not sure I agree with all your conclusions, especially the ‘overkill’ thought, but that’s OK. Differences in opinions is what makes the world interesting. 
 

Specifics, though:

1. Not really. I think you’re getting confused by statements about the PLAYBASE, which includes a smaller ‘subwoofer’ system in it, The Beam does not have that system built in. 
2. Not sure how to answer this. Is a truck better than a car? Not really, they’re designed for two different things, but both will carry you from point A to point B. A Sonos one in a single amplified speaker, that can play either a single channel, when paired with another Sonos One, or both channels as a mono speaker. A Beam is a collection of speakers that can accept a Dolby Digital input and play three distinct channels, front left, front center, and front right. Or, if it’s fed a stereo signal, it can play left from the left speaker(s) in it, and right from the right speaker(s).
3. Yes, absolutely. If the Sonos ones are set up as surround speakers, there are two settings in the software, one is ambient, where they support the Beam, the second is full, where they are regular stereo speakers. In both cases, there is a volume control for changing their volume versus the Beam. Or, if the other speakers are not surrounds, but just a ‘room’ in the Sonos software, they can be ‘grouped’ in the software to play in sync. Since you mention the kitchen and bath, than my latter statement is valid. Note, however, that when not streaming music, but instead using the TV input, there will be a slight delay between the Beam and any other rooms it is grouped with. All the other rooms will be in sync with each other, though. 

Many Thanks 

Most welcome. I hope it helps.

As a reference point, I purchased a PLAYBAR first, then a couple of months later, added a pair of PLAY:1s as surrounds, and finally about 6 months after that, added the SUB. But the order of the last two could have been reversed, depending on my personal preferences. I happened to like surround better, just slightly. But I don’t live in an apartment, and don’t need to worry about the neighbors. The nice thing about Sonos is it’s completely modular, and you can add speakers as you want. I think I’m at around 20 or so, now.…