If I where you, and obviously on a budget, I would amp those subs and build something around those subs, and in the middle of the seat, to keep the seat from touching your subs at max excursion, other wise your gonna end up with torn surrounds, and folded cones, which want be pretty, or sound to nice. Maybe some 1x1 around the sub and in the middle to support the seat, and hopefully not make it to odd looking. Or if no one uses the back much, just leave it up better bass anyways.