If the Fives are being used as surrounds, you can set the Music Playback setting for the surrounds to FULL, and when you stream music, you will get full stereo audio from both the Fives and Beam.

I would test both options and see which one you prefer. Personally, I would choose just the Fives and Sub for music listening in stereo. But if you enjoy listening to music mixed in 5.1 surround, the full Beam 5.1 setup would obviously be the best option. If it’s a Beam (Gen 2) you can listen to music in Dolby Atmos.

Ah I didn’t know gen 2 beam played atoms. So that option with beam, sub and 5’s sounds like best option esp if it’s full stereo audio. I wasn’t aware it was.. 

But it does take an “adjustment” time to get used to stereo music coming from speakers behind you rather than the traditional in-front sound source. 
If you have the system, try both options -it’s easy to reconfigure the Sonos system to try out and see which you prefer. 

I’ve done more research… if you use ATV so that you’re listening to lossless audio from Apple Music (this is the only way at present), the input from the beam to surrounds will be in TV mode so the music playback will be not full. It is only when you AirPlay or listen through Sonos app that Beam will switch to music mode and playback through surrounds will be full. Really disappointing! 
 

This means I’ll likely just go with stereo paired 5’s and sub as my music set up and leave Beam standalone for the TV