Well both, I was somewhat un-impressed with the Fosgate. I am looking to really FEEL the bass, I am gonna try to sell my amp, sub, enclosure and capacitor in hopes of having enough money to buy 1 15" or even 18" if I have the money. * To really FEEL the bass should I be looking at the "BTL" or "BL" * This question seems obvious but 15" or 18" * How would the 18" "BL" compare to the 15" "BTL"