Same question here, i assume it would be the same process if you replaced a playbar with a beam, or play 1s with Sonos Ones, etc.  Can anyone explain what is the proper way to replace speakers in a 5.1 setup with others?  Is it just a matter of disbanding the whole setup and then reconfiguring piece by piece?

Yes, you could replace just the Beam with an Arc.

Yes, unless they put in place a new process in the S2 software, it would be as easy as un-bonding the surround speakers and SUB from the current Sonos sound bar , and then adding the Arc, and bonding the surrounds and SUB to that.

I heard it’s not justifiable to replace Beam with Arc if you already have Sub and rear speakers. You probably get a slight improvement of sound. The side speakers of Arc will be turned off as surround sounds when you have 2 rear speakers. Since you have a sub, it will also take away the woofer effect of Arc.

That’s very odd, all of the reviews I’ve read suggest it’s an outstanding upgrade. Engadget, The Verge, 9 to 5, and others. Where did you hear this ‘it’s not justifiable’ from. I’d be interested in reading a negative review, after all the positive ones I’ve read so far. 

Please click here to view the review

Wow, it seems like a couple folks are really pushing that flatpanelsHD review.  As it is a relatively obscure website, and its review is contrary to almost every other mainstream review we’ve seen, it’s curious why we would have posters pointing out that particular review.

We will see in the next 2 weeks for many reviews in YouTube. I will hold my horses and see whether it's worth the upgrade later

Unless I am missing something, that linked review compares the Arc to the Playbar directly rather than the Beam?

I've a similar setup - a Beam + sub + 2 play1s in a 5 meter squared living room. I found the addition of the other speakers in the group gave the Beam breathing room needed for a larger space. I've no doubt you'll get a similar result from the Arc - as part of a full set it ought to be immense. 

Arc looks very interesting but expensive, at least in Europe. I'd personally hang on for a 10% discount to show up before I bite.

That said if you have the cash to splash, go for it - you can always return it.