sb16 quality outputs vs pro-quality outputs is far less important in your average car because there is so much working against you to start with.

All the more reason to have the best quality you can get in order to compensate.

I disagree with your last point though. The odd shape and soft cloth of car interiors creates a complete acoustic mess...and gives each speaker a different response.

Well... maybe. But the inside of a car is really pretty symmetrical, as are the possible locations for speakers. Are you suggesting that the "...soft cloth of car interiors..." is perhaps absorbing some frequencies more than others? Maybe so... but this is why I have a 20-band parametric equalizer in my empeg, and a pair of third-octave parametric equalizers back with my amps, along with both electronic and passive crossover networks. It's not like the interior of the car is changing all the time (at least, no more than a stereo "room" in your house, with the addition of more or fewer people) and with the right equipment you can compensate pretty well for the perceived inadequacies of the car interior.

I would put my car stereo up against most home audio systems of comparable price.

tanstaafl.