My two cents:
I purchased the Sonos Playbar first...loved the sound, rich, clear and pleasing.
Liking the playbar so much, I added two play 3's for 5.1...those sounded okay.
Finally, I bought the Sonos Sub and holy crap, the system just took off! I have had a lot of very good audio equipment, but I have NEVER heard a sub sound this good. After a few days, I decided to return the play 3 speakers as I just don't think they add enough to justify the $600 cost.
So now, my setup is the playbar plus the sub and the sound is mind blowing. I'm not trying to tell anyone that this beats a 5.1 system or anything like that, but if anyone tries to tell you that the playbar and sub don't sound tremendous should not be trusted for audio advice.
Can you get better sound? Of course you can, but I'm just saying that the Sonos components are very much worth the dollars you pay for them. I would like to know if anyone has compared the Sonos playbar to the Bose SR1 and if so, which sounds better?
Considering the power of the Sonos sub, I doubt that I would make that change. If you are building a Sonos system, the sub is the key to EVERYTHING...without it, it's just an above average soundbar, with it, the sound is epic.