I haven't seen a How To on the steps for replacing the Bose 9" Mid's with something like a 6.5".. I've seen pieces here and there, like mentioning you need to make a bracket? Anyone got a link handy for this? Obviously you need to add an amp so something with suggestions for running wire to the doors would be nice.

 

To run wire to the doors, the best way is through the molex, here is a DIY from member forbidden for this:
http://www.the12volt.com/installbay/...TID~78731~PN~1

As for the bracket, it just needs to be made out of something sturdy, Ive seen them made out of lexan/plexiglass/acrylic/abs plastic. The stronger and thinner the better. I wouldn't use MDF because it adds considerable thickness and might cause clearance issues with the door panel once the new speaker is fitted. Cut it out to fit over the old bose hole, then cut out a hole for your new speakers. Easiest way to do this would be to remove the bose speaker, and trace it out. Then you will have an outline of where to cut for an exact fit and where to drill holes to attach it to the old hole. Then you need to cut a hole for the new speaker.

I would also read the entire speaker sizes sticky and all the stuff linked in that post for some good ideas and info on speaker removal, wiring for power/ground, wire colors.

Here is a DIY I made for the LOC which you will need for a new amp:
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-wiring-4-channel-loc-132087/

If you have the bose, its best to use a powered LOC like the audiocontrol LC6i and wire it in the trunk before the bose amp. That being said, there are numerous opinions on all of this. This is just what I would do if I wanted to replace the bose door speakers.