i know stereos beter than i know engines. puting your subs in your doos is a really really bad idea. not just for clearence reasons. a subwoofer is made to be in an encloser(a box). it will only preform well in a sealed box if there is engough air inside it. in a prted box the port(only one!) cant be bigger than 3in. diameter circle. the reasoning for this all has to do with the amount of travel your sub voice coil has on the cone. if you dont give a box enough air like in a ute door. i know that you have trouble finding space in your pickup for subs, my suggestion is to go with two 10in. subs in a pickup. you will get more than enough bass, and you can use a verry small box with 10in subs because of the travel. with 10in you need around 75-100 cubic inches of air . if you have already mounted the subs in the door then you might want to be carful when rolling your windows down, and dont bother trying to seal it, how ever you could try insulating it to cancel out unwanted vibrations and maintain good vibrations!.
and by the way there is no pioneer in the usa that sells for 700-800 bucks. you got way ripped off. i have a 15in memphis i payed 125 for. a 12in mtx i payed85 for, two 12in audiobahns in a sub zero box for 300. an infinity 15 for 350. wherever youve been buying your car stereo equipment, i would sugest changing you suplier. if you need any other help just ask.
ps. unfortunatly i have spent more $ on my car stereo than i have put into the engine...but not for long