Okay, so I would like to add two new speakers as well as two 12 inch subwoofers to my FJ. My idea is to build a box that would rest behind the rear seats, with the subs on the outside and the speakers in the middle. Before i do this though, I want to get some advice on whether this is a good idea or not. Is it okay to have speakers and subs in the same box? Or should I separate them? Also, would a single port be beneficial to audio quality? Thanks.