Finally, on page 3 we get some sort of idea what you are building here. The whole time I read this thread, seeing choices between serious SPL subs like BTL's and solo-x's to more SQ(L) oriented drivers like the Mags, I was really confused what you were building this for. Now Im guessing you are building a DD SQL system, but using a serious SPL sub. Ive not heard a BTL yet, but if its anything like an MT (and it is, very much) it wont sound that great. Especially if you tune the box to really get loud. And if you dont tune it for raw SPL, I dont see the point of using an SPL sub.Ya, I want the best combo of Loudness and Lows...I think the btl will do the trick...