sauce = source
so in this instance the source is your headunit. it goes from cd ---> digital audio converter(DAC)((in hu) --> eq --->amps, in a very simplified way of describing it. you need a good quality headunit as the speakers can only produce what they are given. the stock deck is pitiful compared to any aftermarket deck. changing the deck alone will yield much better sq to the point you'll hear things in songs you've never head before little nuances so to speak. also you'll want to find one that will give you the ability to go active in the feature so your not rebuying later on down the road.
this looks stockish: Kenwood DPX302 CD Players,MP3 CD Player
there are plenty others that look close to stock and arn't all guady. and there is a company that makes factory looks a likes but with mp3/sat capabilities. i forget their name i'm sure you can find them on google.
i'd get an avn 6620 personally...
oh and your rears are quietey like is because the kickers are less sensitive and need moar power to really shine. buy a $50 amp and you'll be all set.
oh and anything from nakamichi or denon will look stock as well.
these are both good units:
Nakamichi CD-700II - Nakamichi CD Player.
McIntosh MX406 - McIntosh AM/FM/CD Player With Aux Input