If you use your stock headunit/cd-player/changer then the quality of the sound will not be as clear as a aftermarket headunit. Even if you cruise with the "LOUD" option off and the treble/eq settings to a low db (low high's) output, the aftermarket will always sound better. Aftermarket headunits will make cd's sound good with nice high's and some ok bass(thats where the subs come in). So its really up to whether you can afford a aftermarket headunit and/or if you want your system to sound nice with tight bass or muffled high's with loose hitting bass. Reason y it doesnt sound as good is another topic. To lazy to explain y but if u want me to then pm me.