When a pair of speakers are being used as surrounds in a Sonos home theater setup, they cannot be used as a stereo pair without having to disconnect them as surrounds first and pairing them in the Sonos app. Also, only Sonos speakers of the same model can be stereo paired.
Your best option would be to use the Beam and SYMFONISK speakers as your home theater setup and get another Sonos One to stereo pair with your existing One. Then you can use the pair of Ones separately to play music or group them with the Beam/SYMFONISK setup.
Ok thanks for the clarification with this, that helps. I was torn between the Beam and the Bose 300 for TV, swayed towards the Beam thinking i could dual purpose for music using the surrounds. As this is not an option, I have to admit that as a standalone speaker i preferred the Bose 300 to the Beam when carrying out a sound test in a certain high street department store. Back to the drawing board!