Toyota Seqouia 6 15 wall.

[Loud_Low_SuperSlowed]

Currently have 3 PSI Platform 1 15s but deciding to use them in my room. Was thinking of doing a wall as close as i can get to right behind the back of the first row of back seats.

Would be planning on using 6 Soundqubed hds215s running off 2 American bass Ph4000md's. but until i get new alt i will be just running 1 amp. Any suggestions on where to start on this wall? i've never built a wall, due to this would it be easier building a box outside of car, sealing it off from the back of the car? or building the box inside of the car. Any help is appreciated!