I am not a expert by any means and seeking suggestions on a sub!!! First of all I have a small room 12' x 12' with a Marantz SR 4002 receiver with the latest version of Klipsch Quintets and a polk psw110 subwoofer. I went with the quintets based on size and the reviews I had read and very pleased with them and the sub sounds ok!!! But just wondering if it is really worth it to upgrade the sub. The room is a pine side tongue and groove construction with 8' ceilings and carpeted and as stated before limited space so I stayed away from floor speakers and oversize bookshelves. Anyway back to the subs looking to to spend up to 500.00-700.00 will I notice any great difference some I have looked at is the Bic pl200, the svs line, klipsch and even have a friend that has an old mirage s12 and a few others would this be an upgrade or money better spent somewhere else.