I have a new Yamaha receiver connected to my Bose AM10 speaker system. I also have a SACD player connected to the multichannel input. Since I have no powered subwoofer, the sound from the multichannel input has almost no base. Can I add a powered subwoofer to this setup or do I need a new set of speakers and subwoofer? What would be a good powered subwoofer to get?