I am looking for a sub $150 or less for my HT room, 12'X17',6'8" ceiling(acoustical tiles), carpeted floor.It will be used mainly for DVD movies. Would about a 10", 100 watt sub be about right? I saw a Jensen, Sony and KLH on Best Buy's website, are they any good? What's the difference between down-firing and front-firing? Thanks very much, I need your advice.