You should have a factory amp. Mine doesn't have the Bose system and still has factory amps. Mine is located behind the glove box.
Not true. some have them and some don't. Mine is a 04 without Bose and I don't have a factory amp.
Also Just because your amp has 80A worth of fuse, doesn't mean it will ever actually pull 80A. Majority of the time you are looking more like 40A. Unless your at bass comps with it cranked way up on short bursts. Playing test tones and such then yea your going to be more in the 60A + range. And your 4ch will hardly even pull half of its fusing.
When installing the dynamat in the doors make sure to cover up all of the large holes in the metal. your goal is to truly separate the front and rear waves of the speaker.
As far as capacitors go, don't bother with them. spend the money to run larger wires lol. with your current amps you can easily run both of those off a single 4ga wire run and split of to 2 8ga to the amps.