What is your budget? If you can find a used Servo-15 (Paradigm) for a good price, that would be a great match. (I loved mine). Of course, I am prejudiced toward SVS, so that is what I would recommend for a new sub. If you have $14,000 the new Velodyn 1815 is a great sub. If you only have around $125 I owned a Sylvania 12" sub that did quite will. Let us know. Dennis
You can look around for a used sub, not sure you'll find a Servo-15 for $500 though... if you do, jump all over it quick... :T
Consider the PB10-NSD. I had the ISD version in my great room (read huge) and WOTW sounded very good. The new drivers supposedly make this sub even better. If you can stand $600 + shipping... go for the PB12.