I know this has been talked about a good bit, but wanted to put in my 2 cents.  I prefer the ‘tighter’ bass sound of the sub mini vs the full-sized sub, but would also like to have the bass more balanced in my room.  Due to my space, the sub mini is on the far right side and the bass level is quite different when you’re sitting on that side vs the other side.  

End result, one part of the room has a little ‘too much’ bass, while the other side of the room has a little ‘too little bass’.

Having the ability to add a second sub mini would be a great solution to this.  I’m ready to spend my money, Sonos, please add this feature to the sub mini :)