choosing between the 2 5s or 2-300s

Know this first….

Any speakers used as surrounds cannot be used as a stereo pair independent of the soundbar. Meaning the sound bar will play along with the surrounds.

If you want a separate stereo pair apart from the soundbar you must set them up as a separate room. Although they can be in the same space as the soundbar.

Assuming you want a separate stereo pair of speakers for strictly two channel audio the Fives are a better chioce. The Era 300’s are Primarily designed for Dolby Atmos reproduction of sound although they can be used as a stereo pair but IMO are not as good as Fives in that configuration.

Having said all the above if you want full immersion sound to complete the Arc ( with Dolby Atmos) then the Era 300’s are the best choice for movies and music.

Fully agree with ​@AjTrek1. The most important thing is that, for the moment, it’s not an easy job to separate the surrounds and bound them later, as you have to perform TruePlay each time. It’s a 10 minutes thing, so a problem if you need to do it everyday not so much if it’s every quarter.

I’ve the Era 300 as surrounds and the result is an impressive improvement for both, films and music, compared to just Arc+Sub. For music, the Atmos result is amazing. For films, the difference with a good 5.1 not so noticiable.

As a stereo pair, I’m sure that the Fives are much better than the Era 300, but I think the result of the Arc+Sub+2x300 sounds better than 2x5. But in this case could be some people that prefers a classic stereo sound. 

Also just for clarification regarding using Fives or Era 300’s as a dedicated stereo pair. I have both setups in different rooms.

To be clear I’ve been listening to 2 channel stereo since the 70’s. I’ve had the opportunity to experience good (and not so good) stereo separation on many different speakers thru pairs and those used as part of a home theater way before soundbars became a thing and of course Sonos.

Getting to my point my Fives IMO sound better than the Era 300’s in stereo pair. Since being introduced to Sonos I relegated myself to enjoy the Fives as I don’t want to deal with a AV Receiver and wires.

However as good as the Fives are I have an old set of Definitive Technology (Def Techs) 500 towers with high and mid drivers front and rear and woofer powered by a Sonos Amp. They are just too expensive to let sit and dry rot. IMO the Fives as good as they are still aren’t on the same level. Close but not exactly 1 to 1. The Era 300’s don’t even compare up against the Def Techs. JMHO.

Therefore my bias to toward the Fives for dedicated stereo.

For stereo the Fives are the best all Sonos solution. A Sonos Amp and good quality, mid-sized, other brand speakers is likely to sound better, but with wires and at a higher cost.

I am headed a different direction and looking at Atmos as my preferred listening format. Part of that is the immersion in the sound field, that I prefer to the stereo imaging. A second part may well be that my ears are no longer able to hear the quality difference in a CD quality stereo stream and an Atmos stream. How much that difference is, well that's another debate.

Thank you guys for all the feedback. Extremely helpful!

For future searches. The speakers are called Five and Era 300.