What is polyfill? How does it take the "boominess" out of the sub? I am on a tight budget now and am looking at getting a sub for around a 150-200 limit. Does anyone have suggestions about the sub, which I would like to be powered, unless getting an unpowered sub and buying am amp is cheaper???? Also, if the polyfill is definitely worth it, how do you install it? I don't care if it screws up the warranty, but is there a huge risk of messing the sub up?