Finally stuck a multimeter on the speakers in my 03 HSE7. The stock Harmon Kardon system is a 4ohm not an 8ohm as some had thought.

I'm wondering if anyone has re-build the door panels to take better speakers, or found a good 4-channel amp that will fit in the factory location that they'd recommend. It looks like there's plenty of room if I remove the next to useless door pockets and build a custom enclosure. Then I can even put small subs in the doors where they'd be useful vs in the back door where they're always obscured with gear.