If the question is “can Fives bond to a Playbase as surrounds” then they should, though arguably it’s overkill and poor use of the Fives.

https://support.sonos.com/en-gb/article/surround-sound-guidelines-and-limitations

If you’re simply asking whether a Playbase could join the same system as the Fives, and optionally group with them then the answer’s Yes.

Thanks a lot, Ratty, I was afraid that being an old product Playbase will not pair at all (as a surround or a group). I will probably use the setup occasionally, and not aim for perfection.

Initially, I wondered whether to choose Beam 2 or Playbase, as obviously the first offers more options being recent product. But getting Playbase seemed alluring as most reviews say it sounds fantastic (and adds decent bass even without Sub).

It does sound great, but is improved by the Sub. My setup has Sub and Ones for surround duties and is pretty good for music too. Still the big bugbear is poor stereo separation as the Playbase speakers are set close together (an issue with Beam and even Arc too). It’s also better in my home as the tv sits on top of the Playbase.