You could set them up as a stereo pair but you might be happier using them as surrounds instead.

When you play music and want the most sound, switch them to Full from Ambient mode.

Thank you Stanley_4 so in that case which of the three speaker models.would you go for?

For your room size and with the mini-Sub the pair of 100s should be adequate for surround when bonded to the Beam.

Two of the 100s (grouped not Bonded) and the Beam would let you have a very even sound field if placed around the room. If Bonded to the Beam and set to Full Mode or Paired and Grouped you’d get the most sound but you’d see folks close to one not hearing the other rear stereo channel well.

There is a lot of discussion around here on the 300s in music mode and which drivers are active, I’ve not really followed that too closely as I’m not considering them myself. Maybe others can discuss the 300 options?

A pair of Fives would be way overkill for surround but would be great for Full Mode music or as stand alone or Paired for Stereo, I am very fond of my single Five and before I upgraded my pair of Play 5s. They sounded very good and the ability to use them in single speaker, but Stereo sound, was good for filling a room at even volume levels and not having folks only hearing the single channel they were closest to. The 100s would be very similar, just less sound.

If you are willing to skip the surround option a single Five placed across the room from your Beam might be all you need. If not then adding a second Five (grouped, not Paired) and trying to place them in a rough triangle with the Beam should give you pretty even sound levels.

So maybe two Grouped 100s or a single Five, with the 100s giving a bit more even sound levels than the single Five, with the option to add more of either at a later date?

Thank you Stanley_4 for your detailed answer.  Very helpful.