I'm just posting this for other owner's future reference.

I ended up buying a "Stage One" speaker upgrade kit from Bavsound.com. I'm very happy with how it sounds. All the 2 front and 2 rear speakers are the same size (100mm diameter). The Bavsound speakers have identical mounting points (3 total) as the stock speakers. The wiring clip on the stock speakers plugs directly into the wiring harness for the Bavsound version - very much a "plug and play" upgrade.

The front speakers are accessible by removing the small filler plug (about an inch long) that's in the bottom well of the window switch assembly. There's a screw behind the filler plug that, once it's removed, will allow the switch assembly to lifted off the door panel. This exposes 2 more screws that are locking the door panel in place. Once they are removed, it's a matter of using a trim removal tool to "pop" the remaining plastic fasteners loose. I started from the bottom/underside of the door panel. Once a couple have come loose, it become easier to use hand pressure to get the rest of the panel off. There's a short YouTube video (www.youtube.com/watch) that might be useful to watch ahead time.

The back doors are similar, except there's no filler plug to remove. Instead, the door handle has a hard plastic cover which had to be popped off using a trim removal tool starting at the small open slot on the bottom edge of the cover. Removing the plastic cover will expose 2 screws. Once these screws are removed, the panel removal will again be a matter of progressively prying it loose from the bottom edge with a trim removal tool and then using hand pressure.

All of the screws on my doors were Torx T-20 type. A metric socket (I believe 8mm) will be needed to remove the nuts holding the speakers in place.

All in, this took less than an hour to get all 4 new speakers in. The hard parts were figuring out how to get the first panel off and finagling (thank you spell check) the wire clip off the stock speaker.