It depends what type of multi speaker system you want.
If you want multi-room sound you are best off with the Smart Speaker range (or if you already have older systems then the SoundTouch range but they are not interchangable)
If you want multiple speakers for the same room, you can pair two of the SoundTouch 10s for Stereo mode, or any of the newer portable systems (2x Revolve+, 2x Revolves etc).
However I feel a lot of people have misconceptions of what they want and what some speakers are capable of:
- Their best sound at the moment is probably their SoundTouch 30 or the Wave Soundtouch. Different people will appreciate different aspects of these, but you will get much better sound out of an of these than 2x ST10s paired in stereo.
- While two ST10s (seperated) MAY give better stereo, the Home speaker 500 is designed to give you stereo sound from a small speaker by using reflected sound. This is a concept that Bose have been using right from the start even in their best stereo speakers (see 901s). In my opinion the balance of quality and stereo you get from this outweigh anything else in its' size and the only one better for sound is the ST30.
None of these can currently pair with other (non-bose) alexa speakers, but you can use Airplay 2 for similar effect. Again this is generally for multi-room, as if I pair a Home Speaker with an Alexa speaker (or for another example, if I pair the Revolve+ with a Micro) you get an inbalance of sound and quality that really doesn't sound good.
