Thanks. The cabinet on the right also has the same opening as the middle cabinet; we have just temporarily left the original wood in place until we get the sub installed.
I agree with you on starting off with just one. As for buying locally, I really prefer to go with SVS or HSU, and I'd rather run the risk of having to return one of their subs than running the risk of getting an inferior sub elsewhere.
I'd love to get a sub that would look good if I have to set it out, and that makes me wonder about either the HSU or SB13-Plus. The good news is that I have some time to decide. Our house is being remodeled, and we won't be moving back for a few weeks--hopefully by then they will have started rolling out the SB12-NSDs, and I'll have the benefit of early reviews.
I do worry a little about the sound getting lost in the living space, but I also suspect, based on my experience with my original sub, that I don't need as much sound as most of the people on this website to be happy.
So what do you mean when you say I would only be doubling the output? Does that mean that it would get louder, but would not go deeper?