I have definitive bp 7002's with 12" built in subs, I was curious what sub would compliment them, they go low, but I feel I could use a little more bass, I would assume I should look at a 15" sub, but I am no expert on this, looking for some advice, thanks ps I also have definitive clr2500 center and bp 7006 rears. my room is about 16x20