depends if your going ported or sealed....what subs are you using? if its a sub that likes a bigger ported box like 2 - 2.5 cubes per sub, it will be a real tight fit under the back seat and not sure if it can be done. Unless you really like that back seat i would take it out and do subs forward port up, subs and port up, or port to the side with either subs forward or up to get max potential.