I have 2 18" BTL's.. 4k a piece might be a little too much on the electrical, I think I've decided on 2 Crunch GP3000D-Pro's.you'll need 2?? hopefully for seperate subs..or puttin 8000w on 1 btl? lol umm one sold here for $450shipped but theyre expensive new. try woofersetc.com