I have the Dayton dedicated sub amp HPSR 1000 (500 w), and am interested in any recommendations for passive subs. I am surprised to find them scarce. SVS does not make their CS series anymore, and I have not been able to find other models from other companies, at least not ones easy to buy online nor in my price range (<$400). I do not want to build my own nor is IB an option. The SVS CS 25-31 is the one most appropriate for my room and setup, but I have not seen any on ebay, audiogon, or any other used equipment site. Recommendations, information, offers, or any other info is appreciated.