the absolute best thing you can do for your sound quality is to get away from the 2-3 way speakers.
I have been doing custom stereos in my cars since 1993
this is all if you want to spend the money.
2-3 way speakers are just cheap alternatives.
separate highs and mids should be in every location that you want crisp clear sound.
and subs in the rear of the vehicle.
your amp, 2/4/6 channels is all dependent on your wants and your funds.
I prefer to run a 2 channel amp to each type of speaker.
now sometimes in our trucks epically, we don't have the room.
but an amp for each type is the best to tune and get the sound you want.
this is why I do not run head units.
most of my music is digital now a days, ran from my phone bluethoothed into a 7 band EQ.
this way I can adjust the sound quickly and easily.
my system is not perfect, but I used what ive collected over the years.
I did buy rear speakers, because that 6 x 8 is an oddball.
here is my sub and amp set up
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