I have a 3,500 CF room (16x21x10+) with 6' & 2.5' openings to kitchen and 3' opening to dining room. For mostly music and some HT, I think I need one Rythmik F15HP (600W) or two F15's (370W) or two F-12's (370W). I prefer buying the F15HP but am concerned if I have nulls, I will then want to buy a second sub to remedy that problem. If I knew now I needed two subs, I would buy two F15's. I don't really want two F15HPs. Any ideas what the chances I will end up with null problems and wish I had bought an F15 so I could add another one? Aesthetically, I would prefer two F12's if the F15HP doesn't work well.