No, the Era 300s cannot be used as surrounds with the Beam (Gen1)

Under the product FAQ:

Because Era 300 is a multichannel rear speaker, it requires a Sonos soundbar that supports Dolby Atmos, i.e. Arc or Beam (Gen 2). For this reason, Era 300 is not compatible with Playbar, Playbase, or Beam (Gen 1).

I'm really scared to buy the ERA 300 Because just my Luck the will Release the era 500 this year an I would rather have the 500 It has got to be coming the Replaced the one And the 300 So now I'm just guessing they will replace the sonos 5

If you are always waiting for the next best thing, you'll never buy anything.

What do you mean sonos does not come up with products very often At least something I was looking forward to atmos speakers is what I have been waiting for and also the true play for android users is what I have been asking them for and with the economy the way it is looking I can only afford this purchase once and if they replace the 5s or add the era 500 

Maybe look at history and such a bit.

You could look at the Era 300 as a replacement for the play:3.  The play:3 retired in July 2018. 

Sonos said they started development of the Era 300 3 years ago, so 2020 maybe late 2019.

The Five was released June 2020.  So they likely released the the Five knowing they were going to make an Era 300 some day.

Sonos One (gen 1)  was released October 2017. The Era 100 is arguably it’s replacement released 6 (5 ½?)  years later.

Sonos has stated they will release at least 2 products a year.  They stated the release of Era 100 and 300 at the same time is a big deal to release more than one at the same time.  They have stated they have plans to enter 4 new product categories.  Arguable of whether an Era 500 would be considered a new category.

Releasing an Era 500 right after Era 300 would likely annoy a lot of customers who would have held out had they known.

Given that, I’d say an Era 500, if it ever happens, is a good 2-3 years away.

I heard a release date of October 28th I don't know how true that is but that's what I heard

And from where did you hear such a rumour?

There's no way on this Earth that you heard this from anyone who speaks for Sonos.  Exactly what is your purpose for spreading this nonsense?

i never said it was true i said i just heard of it

As I said in my message I don't know if it's true I said that in there I read it on sonos's reddit page

jgatie Calm down We're here to discuss things I said Right in the message I don't know if it's true This is a community everything is up for discussion isn't it relating to sonos 

Sonos have a history of releasing products on a Tuesday.

28th Oct is not a Tuesday

Whatever you heard is complete fabrication.

ok

There is going to be a sonos ERA 500 it oly makes sense I am sure they are working on it