"I just posted this response on a different thread and I thought it fit here as well so I just copied and pasted".
You might want to take a look at MJ Acoustic. For your needs I would recommend either the Reference 100 or the 150 Mk II. The sub I have is the Ref 150 Mk II. They have a small footprint, 12" x 12", have wonderful looking finishes at no extra cost and sound great. The best part of all is they hook up just like the Rel line of subs, meaning they use both a low and high level input that you can hook up simultaneously. They use a nutrik connector cable, also like the Rel line, for the high level input that hooks directly to your amp for seamless integration in a music system. It also packs incredible impact in HT for such a small box. I've only had mine in my system for less then a week but, so far, they sound great straight out of the box. Oh, I almost forgot all three of these subs also go down to 13 Hz. Yes, I said 13 Hz. I would not have believed it but I've heard it in my system. I have my HT/music system in a 15' x 18' room with my system set on the short wall with 8' ceilings but the back of the room is open to the rest of the house. Good luck with you search and keep us posted........John