Depends on all sorts of factors including room size. Why not buy it, see how it sounds, and return it if you’re not happy?

I have full-size Sub with my Playbase and Ones and very pleased with it. 

I would personally suggest to just try the Sub, as there’s always the Sonos 100-day return policy if you’re not happy anyway.

I’m using the Sub-Mini with a Beam (gen1) and One surrounds and it has made a big difference to the HT setup. Very pleased with it. It has a real nice warm tone for such a small Sub.

Thank you. That’s very helpful!

I have a playbase and play 1’s as rears in a small flat - just added a sub mini and find that it makes a really good smooth and unobtrucive addition. I play music : movies at a ration of maybe 70 : 30 - find music to have an extended range and deeper feel while with movies have more punch and I noted clearer voice rendition which I assume is because my Playbase is being relieved of some of its base duties with the Sub Mini in play.

I personally struggle to be 100% clear that I am passing the right data to Sonos via NowTV > Sony TV (quite old) - when I look very often i see PCM 2.0 which I take to be sterio only as the input source. If I play a Bluray movie the surround sound is amazing - well defined and orders of magnitude better than anything streamed - which I take to mean that the data you recieve via streamed content just cant contain the same quality as that you can have via Bluray…

Unless I am doing something wrong or my telly is too old and not passing things to my sonos speakers - even if that does not make any sense as the Bluray player is passing throught he telly fine.

I do have Boost on my NowTV account - but this is at a tangent - the Sub Mini is great - go for it… :)

@scottdougall .  This is also off at a tangent, but I have just given up NowTV (including the Boost upgrade) in favour of the newly launched Sky Stream (with UHD/HDR/Atmos upgrade).  Very pleased with it, but whether it’s worth it for you will depend on what sort of package you want.  I have Sky (until recently through NowTV, now through Sky Stream) mainly for Sky Sports.

Edit.  If you have an old TV then Sky Glass may offer better value.