I don't know what size subwoofer to get because our listening area is part of our kitchen and dining area which makes it a very large room but on the otherhand I believe our den area is only a medium listening area if you consider the seating area.
Well the sitting location is about 14 feet from the receiver and center channel etc. The room is about 16X16 ft but behind the sitting locations it's a lot more because of the kitchen and dining room probably more like 25X25ft.
btw after posting this I decided to break the budget and bought a VTF-1 from HSU...I hope it was a good decision.
Stang, that sub is quite good at music, suffers a bit if you whack the volume. If you are normal, that sub is quite good. The price don't kill ya neither, good buy.