I just bought an old JBL PB12 off of ebay for $42. The JBL amp has blown and the guy had put a 40watt KLH amp in its place. Well this sounded like garbage. I currently have a B.I.C. VL1220 and I would not have bought the JBL but for such a low cost I figured it would be a fun toy. My first question is should I put another plate amp in the box or should I just seal the box and use an external amp? Would I be better off trying to have the original JBL amp repaired? Also should I fill the box or just leave it empty? Last question is should I change out the sub?