I don't dispute that you've owned 7 Sony head units in 13 years without a problem. It doesn't mean anything if that means you buy a new Sony head unit about every two years. Pretty much ANY head unit will last two years.
I don't dispute that you can make a Sony head unit sound good. In fact, I believe that you can make pretty much any head unit sound good. I have a Mazda CD player (pulled from a 2000 Protege) in my Mustang and it sounds good. That's because the Mustang has dash speakers which I replaced with aftermarket 3.5" two-way speakers and now it has very good high frequency response and good stereo imaging. That just goes to show that the speakers and speaker location are more important than the head unit.
One thing I have seen that differs between head units is the FM sensitivity/selectivity performance, but if you mostly listen to CDs, do you care? Or in the case of tape head units, Dolby B or not. By the way, it's amazing just how much you have to pay for an aftermarket tape head unit to get one with Dolby B on it when I've never seen a single factory tape head unit that didn't come with Dolby B.
I don't dispute the fact that Sony head units aren't returned to Circuit City any more than other brands. I don't think this means anything because nobody is going to return their Sony to Circuit City if it's 3 years old when it breaks.
Well, one post said "So what if it breaks when it's 4 years old, by then you want something new anyway". I guess if that's what you want, why wouldn't you be happy with a Jensen? It'll last at least 4 years, probably. If not, it was only half the price of the Sony.
I want to get rid of my head unit because I'm sick of it, not because it broke. It might take longer than 4 years for me to get sick of it. I'd still be using the factory CD player in my Contour if it hadn't crapped out.
As it is, I have a 6 year old Kenwood CD player in there now which works fine.
Can one expect that sort of reliability out of a Sony, if one doesn't want to replace their head unit every 4 years?
