Hello, I am curious about Subwoofers. What I mean is how do you pick out a good sub? My room is small - 19x10. Ceilings are very high in this room, They arc to about 14'. I'm currently using a Polk PSW10. I was watching The Fellowship of the Ring yesterday and the sub just couldn't keep up. It was rattling, but not the good kind. I think I want to upgrade to something that can produce a rich sound w/o the rattle. I'm don't need something to shake the entire house either. Any recommendations for upgrades would be great. My budget is around $300.