Title covers the important part, but time to fill in all the little details.
I have been bitten hard by the car-stereo upgrade bug. I currently have the base-level stock stereo in my '00 Mustang GT. I got some Polk EX 6x8s back in '03, and they did it for me for a while. Now however, I plan to put a single 12" sub (free-air) on the (reinforced) rear deck, move those Polk EX coaxials to the front, and power it all with fresh wiring and a good 4-ch amp (probably a Soundstream TRA680.4) off a new head unit (probably the Clarion DXZ475MP). All this (depending on the sub I use) should only run me ~$500 or so.
The thing is, none of it can happen until I figure out a way to get those Polks into the doors, unless I want to destroy/run them as passive radiators for what ever free-air 12" sub I end up putting on the rear deck. I thought I could cut out an opening in the bottom-front corner of the door panels (the area that covers the stock door-mounted 6x8s) in order to remove those stock speakers and put in my Polks. I could then make a brazed piano-wire "grille frame", cover it with black grille cloth, and either glue or screw that grille in place over the "access panel" I had cut out. This could work, but sounds like a crap load of work.
I thought about buying a set of Q-Logic kick panels, plus a ~$100 6.5" component set, and scraping the Polks in favor of that setup for the front. That may be easier (though Q-Logic kick-panel reviews indicate it may not be easy at all), but it is definitely more expensive. My project cost would go from ~$500 to ~$800. That large a difference just doesn't seem reasonable, especially since I already own a pair of Polk EX 6x8s, and I really do enjoy their sound. They're not perfect, but they are pretty good.
Anyone with other potential solutions? The cheaper the better. Maybe someone has had to cut into glued-on door panels before? What should I do!