It’s not really clear-cut.  But I would go for Sub and two One SLs.  The Fives would be rather wasted for the surround sound.  The Sub will make a big difference for both music and TV sound.  You will need to set the surrounds to play FULL rather than AMBIENT sound for music.

(I don’t agree that traditional amplifiers and speakers have had their day, btw, but that’s another topic…..)

thx John.  if ignoring the tv and just for music,would you go for 2x 5 or 2 x1 and sub?

That is a topic for ongoing debate on here. You will find that there are supporters of both possibilities. 

So this is very subjective but my vote would go (just) to a pair of Fives. I think it gives a fuller sound, with more than enough bass capability for my tastes.

You need to be aware that if you wanted to listen just to the surrounds you will have to unbond them from the Beam, which is a bit of a faff.

It would need a high upfront payment, but Sonos offer trial periods in many regions. If you qualify for that, then buy the kit, try it in your home, and return the “rejects”. And update us with your views on the two systems. 

I have an arc, a sub and two one SLs.  Although I’ve not compared that AV experience to just a pair of 5s, it’s a pretty good (not fantastic) Atmos experience- and with a little tweaking listening to music also sounds ok. I think if you don’t have an AV experience that’s at least 5.1 (ie requiring some soundbar) you’ll be disappointed.

Of course with effectively two pair of stereo speakers and a sub listening to music - imaging will be a problem, but for most casual listening it sounds fine. 

Thx all.  Very useful (nik9669a I particularly like your idea of trial and return, although unfortunately not possible).  One combo I wondered about (at least as an interim) - how would sound beam and sub woofer work?

C

I went with arc 2 play one's and sub for movie watching and 2xfives plus sub for music as music sounds better in stereo to me

Overkill I know but each to their own