Thinking of adding (2) RP-10 subwoofers to my 2-channel setup with forte IV as the mains. Would I be better off with a single RP-12 sub? Would a single RP-10 be enough? Looking for recommendations from anyone who has experience with the new RP sub line. I listen at low to moderate volume levels. 80% music, 20% video/movies. I do not need to break the 20HZ barrier. Just looking for that extra lower octave or so. TIA.