Thermals1,
Mine are in a room that is 24' x 26'. I've had subs for several of my setups over the years and after going thru the heartache of getting them working well, enjoy having them.
The bass that the Sopra's have is very good, but IMO subs add a lot to the extreme low end.
I'd recommend, if you get the Sopra's you do so without subs and get them really "dialed in" to the room. In my case, in my "man cave" I found they sound the best when pointed in, "focused" just in front of my listening position. I've never placed any of my speakers that way, but the sound stage is just awesome in that room, pointed in so much. When listening to the Beatles, it sounds like Paul McCartney is standing right in front of me singing!
I have a tube preamp, solid state power amp, and a pair of JL F113v2 subs...very much overkill, but I love the sound! I can listen to this setup for hours, never get fatigued.