I think you’ll have to break the stereo pairing first.
@nik9669a is correct. You have to unbond them as a stereo pair before you set them up as surrounds.
FYI… a pair of Play:5s as surrounds for a Beam might be overkill. The Play:5s could overpower your Beam. A better option would be two Play:1s or One SLs as surrounds.
Thanks a lot for your answers, very helpful
It seems you have to choose between surround ou stereo but you can’t have surround when watching TV/movies (with the Beam) and stereo (only Play-5s paired) when you just want to listen music, right?
Yes, once you bond the Play:5s as surrounds to the Beam, they will only play as surround speakers. If you want them to play as a stereo pair again, you have to unbond them from the Beam.
While playing music, you can set the surrounds to “Full” or “Ambient” mode. Most users set it to “Full”.