Hi

Without a doubt the Era 300’s will make an improvement over the One SL’s even if you’re not interested in full immersion with Dolby Atmos.  The Era 300’s complete the Dolby Atmos experience as they too are capable of rendering surround audio encoded in Dolby Atmos which the One SL’ s are not.

If you are not interested in Dolby Atmos then a less expensive upgrade are Era 100’s which replaced the One series. The Era 100 has two angled tweeters above a mid-woofer. The One SL only has a single tweeter and mid-woofer.

I find my Play 1 set and One SL set of surrounds more than meet my needs but I don’t do much Atmos or I’d sure see that differently.

If I did Atmos I’d think the upgrade to the 300s for my Arc room would be a given, that would make a huge audio location perception difference, probably wouldn’t set them to play louder than the current Play 1s though.

In my Gen 1 Beam room, the location requirements for the 300s pretty much rules them out. If I upgraded to a Gen 2 / Atmos Beam I might buy a set with the 100s and a Mini-Sub using the Sonos Upgrade discount but only if I could re-home the originals.

Yep..same setup as you. Bought the Era 300’s. Returned them two hours later to Bestbuy. 

We did last year and honestly the biggest difference we noticed was with non-Atmos content.  The soundstage becomes much wider and the sounds no longer come from specific points, rather they sound like they are all around the room.  Atmos does improve as well, but for us the non-Atmos was the biggest surprise.

Did you find the 300’s weren’t as loud as the One SL’s?