I've decided to drop the BTL's and go with Type R's from Alpine...I've heard three sets of them and they are plenty loud for me. The thing is, I want to make it a nice clean install, so I want to make a ported box to fit, but have room in the back for the amplifiers + room to access them. According to the users manual, the optimum box ported is about 2 cu ft for one. I've already measured & I can fit a box 36" wide & 16" high, but I don't know how deep it would have to be. Anyone have any insight on what to do? I'd appreciate it. Thanks