Not enough room as in my box is too small?i think you dont have enough room man..get rid of the 18", get a NS 15" rebuild the box and youll probably be louder ..this is coming from someone experimenting with 15's 18's and ext cab trucks //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif