You can do that.  The Era 300 would be setup as a second Sonos room that can play audio with yor existing room (Fives) or separately as desiged.   Hard to tell if that’s the right decision for you without knowing more details about the size of the spaces, aesthetics, and your listening tastes.  The Era 300 is for atmos music and medium sizes spaces.  It may make more sense to get a pair of Era 100s instead.

Thanks for that input!  I will investigate the Era 100 alternative, as I hadn’t considered that.  

If you want Stereo sound in the kitchen, you may not if you can’t be in the sweet spot then a pair of 100s is the way to go.

I’d look at a Five, maybe up on the cabinet tops as that gives you a lot of sound in what may be a noisy room.

A single 100 is plenty for background music but two, in mono mode, might give you more even sound.

I’d sure unpair my Fives and give one a try before buying anything else.

Thanks, Stanley 4!  I’ve been so impressed with the room filling sound of the Sonia Five pair. The space has high ceilings with many angles. It’s hard to predict how sound will carry, and the Sonos tuning deals with that very well.