Email or call Vince at Totem. He has been very helpful with me and will be more than willing to answer your questions. Also, see the thread re: Velodyne v. Rel. It might prove helpful. Probably not much need for the DD-15 though unless your room is huge. The dd-10 and 12 are both amzingly fast and all the base you should need. Vince will likely suggest the Totem Thunder Sub, but I've haven't heard or seen any reviews on it.
Personally, I really like the winds. I have the forests and would love to upgrade when I get purchase the power to drive the winds. As mentioned above - Mani-2's are also a great choice. You can't go wrong here with either speaker choice or either sub.