remove the rear seats?
 

what does it take to do this, i have a sub box and i need to try to put it in through the back seats.

1. Pull up hard on the front of the seat to unseat the 2 clips holding it down.
2. Remove 2 bolts (11 or 12mm socket) at bottom of seat back.
3. Lift seatback to unseat 2 clips holding it at the top.
4. Untangle seatbelt.

The following thread includes DIY info on removing the rear seats: https://www.rx8club.com/series-i-do-yourself-forum-73/diy-how-replace-rear-6x9-speakers-9991/

Hope that helps...