I found a Crossfire group on the internet and soon discovered a fix to something that I had been bothered by - the muddy bass from the door speakers.  The fix was to simply put in a capacitor to act as a crossover cutoff and clean up the bass. 

 

This cost 11 dollars and took less than an hour.  The results were superb and well worth the small investment in time and parts.  It was so easy a beginner could do it with a wire stripper/crimper and eight connectors.