Reading cb56's dilemma (a lack of slap-your-chest thump in his current Bag End rig) got me wondering: How small and portable can you make a subwoofer that's suitable for a 1000W rig? I'm thinking along the lines of a powered sub that could be added to a "normal" fullrange stack when needed, covering 100 or so Hz and down. I know there's stuff like this made for home theater rigs, and I've even seen a homemade one made from Sonotube! (http://www.hometheaterhifi.com/volume_6_3/diy-11-sonotube-subwoofer-september-99.html) Could such a critter be built as a single 15? A single 12? A single 10? What kind of power would you need to push through the thing? Would it be PRACTICAL?