Having gone through 2 beaters in a very short period of time I decided that I needed a decent daily driver that was large, comfortable and got decent mileage. It didn't take long to narrow it down to a w123 chassis Mercedes Benz.
The early 1980's technology 'sound system' was lacklustre, to say the least, so I set about improving the quality of the sound. I listened to a variety of combinations of speakers that would fit in the stock speaker locations without molesting my car and eventually chose MBQuarts. (Unfortunatly I knew very little about car audio at the time and chose co-axial speakers for both the front and back.) I also bought a Pioneer 300x4 amp to ensure the speakers would have enough power to reach their potential. To power the JL subs I had left over from a previous system I bought a pair of Pioneer 300x2 amps. Finally, I picked up an Alpine 7894 head unit to replace the stock Becker tape deck that came with the car.
Here's a quick overview of the system:
Head Unit - Alpine CDA 7894
Amplifier, Front - Pioneer GM-X364 300x4
Amplifiers, Subs - 2 Pioneer GM-X562 300x2
Speakers, Front - MBQuart 4" DKD 110
Speakers, Rear - MB Quart 5.25" DKD 113
Subs - 2 12" JL Audio W1
Alpine head unit installed in the stock location.

JL Audio Subs in a generic box in the trunk.

Sub box pulled forward to reveal the amp rack.

Close up of one of the Pioneer amps and the distribution block.

w123 Mercedes have a sound proof and air tight trunk, which prevented me from hearing anything from the subs. To alleviate this problem, I removed the first-aid kit from the rear deck. I've designed an aluminum grill, similar in style to the stock rear speaker grills. After I've machined it on one of the CNC machines at work, I'll hard anodize it black to make it appear stock.

As you can see by the previous photo, it's raining. Thanks to the rain, my car is quite dirty, so I don't have any exterior shots yet. Next time there's decent weather I'll get a couple of photos of my car. Being that this is Vancouver, it could be a few weeks.. or months! :p