All of my speakers are set to small, with my sub set to on (no sub+L/R). With an SMS-1, this is probably the best way to approach it - in fact, it would be almost essential if you wanted to really see what the sub was doing by itself.

We were watching a couple movies this afternoon while doing other things in the den, and in teh middle of Italian Job my wife remarked that the system sounded better and asked if it was because of the SMS-1 (the only thing that has changed in the system since last May or so).