If you are using a Sonos sound bar like a Beam (Gen 2), you can only add up to two Subs (one must be a Sub Gen 3) and two surround speakers for a 5.1 (or 5.2) setup. You cannot connect four surround speakers.

So you would need the Beam, Sub(s), and one Sonos Amp to power your two in-ceiling (or in-wall) surround speakers.

Excellent, thanks for the quick reply. How effective is the Beam with atoms experience?

I haven’t personally tested the new Beam, but from the reviews I have read, Dolby Atmos audio from the Beam has been reported to sound really good, but just don’t expect to hear convincing height channel effects since the Beam doesn’t have any dedicated upward firing drivers. If you want a more convincing Dolby Atmos experience, especially from the height channels, consider getting the Sonos Arc instead.

Thanks for your advice. I got the Arc with 2 surround ones and a sub. Did the true rest sound set up this morning, looking forward to listening later. 

After reading about surrounding speaker and really hope SONOS can consider ROOM for surround connection as the size and protable make a advantage..