I wanted to post these only after the install was entirely done, but I'd have to wait at least another month before I'll have time for that. So, here are the first pics of my 4+ month "install from scratch" in my 2002 Mercedes-Benz E320 wagon.

This was my first install. Thanks to so many of you, I learned how to use a voltmeter, how to solder, the different wires in the harness, and much more. The install uses the stock Bose amp and speakers to keep the install cheap (~$80 in parts total) and "quick". Information on how to do the install was scraped together by the few people who said it was possible among the many many who said it was not (including an empeg installer from this forum; my main inspiration to try it).

Still to come:
Super stealth face place (and better pics of the Alpine's stealth).
Custom Volvo/Benz animated logo (for interop between my two cars).
Increase amp gain.
Take pictures with Filener yellow lens gel and green buttons (to match both the Volvo and Benz).

The wiring harness, carefully researched, tested, soldered, and heat shrunk: