My RCA RT2500 receiver has a builtin amp for the passive sub. I would like to know if the output is already low-pass filtered, or if the crossover is built into the passive sub enclosure. Im thinking I can just connect one of my bookshelf speakers (100w,6 Ohm) to the amplified sub output (200w into 3 Ohm). If I hear nothing from the tweeter, then the sub output would be filtered, correct? Would this possibly damage my speaker or amp?