Well, it didn't take long to blow the last two factory Boston speakers - the foam surrounds disintegrated under pressure. Lucky they were very simple to replace. The door cards are held in with a handful of screws and a few plastic clips and came off easily. The stock door speaker was a 6x9 so a cheap set of Sony on sale slotted in nicely. This got rid of the last of the buzzing and now it sounds something like I envisioned when I bought the car. Gratuitous shot of the car back in the shed just because I love the look of it.