Don't overlook Audiofreak32's mention of Dynamat. Lowering the noise in the passenger compartment is an essential first step. In my last car I lined the doors and inner door frame pillars with Dynamat and had substantially quieter environment in which to listen. BTW, I've got Focals and find them very satisfying.
Car Audio Speakers
I know this rarely if ever pops up on Agon. But I'm in the market for speakers for my car. Anyone have any experience with high quality car audio speaker brands that can rival audiophile speakers? I'm pretty clueless. Most of my experience in car audio comes from those idiots who blast their distorted one note hip hop/rap bass at an intersection on weekend nights.