Your decision is unrelated to choosing between either of those subs. What year Silverado? If its the OBS you have much less space than the NBS. If it is a NBS, I'd step up to a single 12. Either way 2 8's ported isn't going to make box building so easy. Why do you generically think it matters? Why do you always offer what you have? Its really simple. The box alignment should be determined by the driver you chose. Just stupid to choose a driver designed for an alignment and stuff it into something different. He showed pics of the seat M5 ... late 90s just like mine ... You sure a 12 will fit under there and have room to breathe ??? he wanted to stand up the subs to the front of the seats, so how could you even reccomend a 12 and take up all the rear seat leg room ??? I just mentioned to him about my downfire setup to give ideas ... I was only wondering why he wanted sealed ??? I have a Blow Thru enclosure, not a under the seat enclosure, you know that ... and I never gave a driver suggestion ...