Yeah, it's big what just swapping speakers will do for you..
But unfortunately, I'm starting to be convinced that the absolute most difficult thing for a car stereo to reproduce, is god-damn AM Radio
I think it's because male vocals resonate greatly with door-panels. You really need to do something about that aspect if you can.
My 2cents for a good car setup:
A bit of CLD is a good place to start to reduce those door panel resonances.
Road noise is of course an issue, because it raises the SPLs you try to force out of your driver. Mass Loaded Vinyl + Closed Cell Foam are never a bad idea in the doors, and anywhere else you can put them.
As far as speakers go, I think what you need is a larger driver that can cover as wide a range as possible. Something like this in a box:
Scan Discovery, 10F/4424G
Aim them so they cross in front of the middle driving seat it will be directional in the treble. That's got its pros however as it should improve imaging a bit . The main thing is that it's covering much of the whole midrange without space issues. If you need to add a supertweeter, that can be your call. I wouldn't bother.
Add in some decent 6.5" woofers to cover 100hz to 400hz. Don't need to go overboard
Dayton RS180S-8 7" Reference Shielded Woofer 8 Ohm 295-364
And cross them together near 500hz to your woofer, digital/actively with as much control as you get. Ability to measure is of course very important. Something like a miniDSP:
miniDSP 2x8 kit | miniDSP
Will handle this part.
Finish it off with a decently sensitive subwoofer, like this,
Peerless 830669 12" Paper Cone SLS Subwoofer 264-1118
in as large a sealed box as you can personally deal with, that will benefit greatly from pressure vessel gain inside the car. If you can mostly seal off part of the trunk, that may be best. Sensitivity in the 50hz to 100hz region is probably a lot more useful than deep extension, as you don't really want to need a lot of power for the sub.
The hard part? Figuring out a place to put the 3.5" mid-tweeter and an "enclosure" for it.
System: Marantz SR6003
---> Crown XLS 2000 ---> Philharmonic Model 2
---> Tapco Juice J2500 --> DIY Maelstrom X
Victory goes... TO THOSE WITH COURAGE!!!