i agree with building it yourself, if done right will be better and MUCH cheaper then anything you will find out there, only takes like half a day to complete a whole box start to finish
i wanted a box that would hold 4 10" subs right behind my seat and have the option of running all 4 or just 2, so i had 1 amp for each pair of subs on switches, worked really sweet, because each pair had its own compartment so the air space was correct
i can run down everything u'll need if u really need me to , but if its Song Xplod on demand or JBL, whatever, custom done right will always sound better
got pic of mine if ur interested, cause i'm selling it
good luck