They will sound better but the difference will be best heard on the Era 300s when playing Spacial/Dolby Atmos music, which I believe will only be via Amazon Music HD out of your streaming services. Whether it’s worth it will also be down to the size of the room they will be in too - Era 100s will be sufficient for a smaller room but if you have more space to fill then get the Era 300s.

I just live in a small flat so room not massive so maybe just two more 100s then. Not too bothered about Atmos. I’m just curious as to how much different 300s will sound. 

I find the 300s seem to fill the room a bit more on Stereo content and have a bit more low end.

If Atmos mattered (I was not interested but now that I have 300s I’m hooked) then the 300s are a must.

Anywhere you can go to do a listening test? Not so much an in-store on/shelf display but a listening room?

I have both Sonos 100s and 300s and much prefer the sound of the 300s, either standalone, or stereo paired. They sound great when paired.

My own choice, if money was not an issue, would be to go with the 300s. If you purchase direct from Sonos there is a no quibble money back guarantee if you decide to return them. See link:

https://www.sonos.com/en-us/legal/terms#legal-terms-sale-2024-returns-us