As a diehard Chicago Bears fan living in New Hampshire, I am working on setting up a TV room in my basement. The room is 22X13 and the ceiling is about 7 ft. I currently have a Parasound HCA 800 amp running through a NAD 7100 receiver. My speakers are a pair of Totem mites. I am interested in adding a sub to get more lower end. My budget is about 650 dollars, and I would like to purchase a used sub. Any thoughts?.