4.0B2 is on the right track about the amp explaination. A class a/b amp passes high, mid and low frequencies where a class d ONLY passes low frequencies. I have a BS in electronics engineering. Trust me on this.
Here is my set up.
Speakers and amp:
Kicker DS68 6x8's (I believe that is correct)
Kicker ZX500.1 Class D Mono Block amp
Kicker Solo Baric L7 10" sub in a custom built fiber class enclosure (Still needs to be purchased and built)
My head unit:
Sony XAV 62BT
You have to invest in quality parts to get a quality sound.