As mentioned, that 600c is a monster .... maybe scale it back to the 200c if size is an issue.
I just listened to a recent kef HT system setup in a basement consisting of Q500 L/R, Q600c, Q300 surrounds but I forget the sub name right now. Overall sounded like a nicely balanced setup, I enjoyed the sound. Last I heard the owner was going to order Q900 but that was probably due to his music uses more than HT.
Steve