You cannot have separate front left and right channels.

The Arc will always be front left, right and centre.

The Arc, just like every soundbar ever made, is not a center channel speaker.

Ok thank….too bad!

Use the system as intended. The Arc has side-firing speakers that give surprisingly good separation. You could use the Play:5s as surrounds (assuming that they are gen 2s).

However, I'd recommend getting One SLs for surrounds and keeping the Play:5s for music.

Exactly.

BUT, for a music solution (music only) should it not be possible to make the Play 5’s a stereo pair and place the soundbar in the middle? In this case, you’d have left/right stereo separation and in the center left/right/center. It should work, but in practice it might get a bit busy. Have to try it.

Anyone out there with two Play speakers and an ARC that can try this, I’d love to hear from your experience. 

It is certainly possible to group a pair of Play:5s with the Arc, so they all play music in sync.

I have Fives either side of the Arc for music playback only.

It all comes down to personal preference. I prefer to only use the Fives for better stereo separation. You may like to have the Arc grouped and listen that way.

Just set them up as a separate “room” and group the two rooms. You’d still be getting left and right out of the Arc in the center, so your sound stage would likely sound a bit odd. I’ve grouped them before in my setup, but only when not doing any critical listening. Might be useful for parties, but then I’d usually prefer to have a bunch of mono speakers in use, since people are moving around, and not sitting in the “sweet spot” of a stereo image. 

There’s certainly nothing stopping you from testing this. And probably more useful, too, I’m pretty sure my ears are different than yours. 

What you can do is setup one Sonos room in your space for home theatre.  An Arc, 2 surround speakers, and 1 or 2 subs.  Then a second Sonos room in the same physical space for music playback.  A pair of 5s + sub maybe.  That would give you the best of both worlds for music and movies, and many people have done this.

You don’t really want to group these two Sonos rooms together though for a couple reasons. Start with home theatre/TV sources first, your HT room will play the audio immediately to stay in sync with the video, while the Fives will play it slightly delayed for buffering reason.  The result is an ugly echo effect.  You also are not really taking advantage of trueplay tuning, since each room is tuned to the room without consideration of the 2nd room playing at the same time.  And you would need to control volume of both rooms.

If your source is music, then you avoid the echo effect, but again, not really using trueplay and you have 2 room volumes to control.  Whether it sounds better is a matter of personal preference, but I’m not a fan of it personally.  I prefer stereo with the wider base, and having the same audio channels coming from a soundbar is a distraction.  As maybe a side feature, my HT room is always set to play TV audio, and volume is with TV remote.  I never use it for whole home audio, really, so I never switch sources.

It should be noted that a sub cannot be shared across two rooms, so you would want a sub or two for the HT room, and a sub for the music room setup.  If you don’t want to buy two subs, then you may find using the Arc + sub is better than 2 Fives without a sub for music, particularly if bass is important to you.