Play 3 replacement

The Era 100 is the closest current equivalent, IMO. I prefer the sound of the Era 100 to that of the Play:3, insofar as I can remember how a Play:3 sounds.

The Sonos One would be another  good option, at significantly lower cost.

I haven't heard the Era 300 yet. They are being delivered to me tomorrow! I think these would be a significant upgrade from the Play:3. I'll know more soon.

If you don’t need the added features the One has, the One SL would be a safe choice.

The 100 is still a bit new and I haven’t heard one but I’d consider them too.

If you're looking to add a similar speaker to your existing Sonos Play 3's, the Sonos One (Gen 2) is a great option. It offers similar sound quality to the Play 3, but also includes voice control with Amazon Alexa or Google Assistant built-in, as well as Apple AirPlay 2 compatibility. The Sonos One (Gen 2) also has a sleeker design compared to the Play 3.

If you're looking for a more powerful speaker, the Sonos Five is another great option. It offers more bass and a clearer, more detailed sound than the Play 3, making it a great choice for larger rooms or if you're looking for a more immersive audio experience.

The ERA 100 and 300 are also good options, but they are not compatible with the Sonos ecosystem and do not offer the same level of integration and ease of use as Sonos speakers.

Ultimately, the best choice depends on your personal preferences and budget. If you're happy with the sound quality of the Play 3 and want a similar speaker with modern features, the Sonos One (Gen 2) is a great choice. If you're looking for a more powerful speaker, the Sonos Five is a great option.

First it would be useful to know what sound bar you’re using for a start. If you have an older device playbar, play base, beam gen 1, you can only connect play 1, one, one sl, and fives. If you have the arc or beam gen 2 you can connect all previously listed as well as the era 100 and 300. Both era speakers are wonderful additions as surrounds, but the 300’s are definitely suited for atmos content. The era 100’s are a definite upgrade to the ones, but still a smaller soundstage than the play 3 (you can’t beat physics). If you have an atmos capable soundbar the era 300’s are a no brainer if you can stomach the price tag.

I am sorry, but that is totally incorrect.  The Era speakers are fully part of the Sonos ecosystem, although naturally only with S2, not S1.  The Era speakers ARE Sonos speakers.