1. Yes.
2. You could easily enjoy the M22 bookshelf without a subwoofer, whereas the on-wall M22 needs one.
3. EP125 was designed for small rooms. Yours is around 2160 sq ft. The EP175 was designed for rooms 2000 sq and smaller. But it should have enough bass for the on-wall M22. I've got an EP175 on order that I will be using with on-wall M22 in a 1800 sq ft room, so I won't know for sure until I hear the combo.