UPDATE!!!!!
After being away most of the year, I took my car to the local Dodge dealer. They diagnosed that the sheet-plastic moisture guard was touching the speaker and causing a secondary vibration, which I mistook for distortion. Their fix was to trim the plastic out of the speaker opening, leaving enough to still trap under the speaker mounting flange. Two weeks later, it still sounds great! I took the opportunity to test drive a new Magnum while mine was in the shop. Looks like a hemi in my future to replace the wife's old Taurus wagon! The Chrysler dealer who refused to look at my problem just lost a customer to the Dodge Boys! [?]
