Have you tried the "bass crawl" technique for positioning the sub? Put the sub in your primary listening position, play some bass heavy music, and crawl around until you find a spot that has good bass (tight, clear, loud, etc.). Then switch positions, you back in the chair and the sub where you found the good bass. You should now have the good bass you heard in the primary listeing spot. Placement is crucial, as I found out, since there are a few dead spots in my room where almost all the bass cancels (which sounds like your situation).
Just to ask a dumb question, is the green light 'on' on the back of the sub? If its yellow or not on at all, then something's not giving it power.
