Just wanted to throw this in... JL Audio makes a 13" subwoofer which is super shallow. In fact I have seen a previous owner who had 2 of these in the stock sub locations (ofcourse with plenty of mods) and I personally own one of these subwoofer (except its in the rear). So it is indeed possible (and not just with 13" shallows!), but it just depends on how much work, time, and money you want to put into the project.. personally that sounds like one hugeee headache. I agree more with the "buy a new amp and speakers"...