I have a 2003 Explorer with factory 290 watt 6cd changer and subwoofer. It sounds OK and looks good in the dash. I googled many times trying to find out more about the system but got nothing. I would like to add HD radio capability and tighten up the sound and bass. Using Crutchfield I found it has 6X8 spks in the doors and an 8" subwoofer. They have some 6X8 Infinities with postionable tweeters at $75 pr rated at 4ohms. Would I be happy replacing the stock speakers with these and what should I do with the subwoofer? What would you do with this system and $500?