1 sub behind seat, sealed not ported. like jaybo said, they sound better behind seat. cc's just suck balls for subs, so putting them behind the seat usually calls for a shallow mount. the new rockford p3sd 10's sound very good, only 3.5" mounting depth. if you wanted to, id go for the sundown sd2 10's, nicer sub and still only 4.5" mounting depth. you do need to take into account cone excursion when box is built, so the surround and cone dont hit the back of the seat.