Well, you have the space for both boxes?? i don´t know much about durangos, but i do know a little bit about those 10" pioneer subs, i built a friend´s scion XB a few months ago, a piece of junk hifonics hfi2500D amp with a 140 amps alternator and single kinetik HC1800 battery on the front, he wanted to play as loud as he could with that amount of power and didn´t care about numbers that much, i ended up building 2 subs front/2subs up with port side box, 6 cubic feet after displacement and 84SQ of port, let me tell you, that shit sounds AWESOME!!!!
It´s loud as hell, plays very nice on every song we play, and best of all, scores 146.7 dbs sealed on the dash without any flares, 45´s , resin or anything, i know i it has at least another db on it if i get some more work done, but yes i really love how it plays, funniest thing is that he has 200$ on subs and beats a lot of guys with much more money on subs.
I can´t say 6 subs of those are gonna be louder than a single 18" BTL, i honestly think a BTL would murder them, but damn, they are way cheaper and Also, wow factor FTW hehe.