Tried Using The Harness With The Rca Cables On It But It Still Sounds Bad.could It Be The Speakers?

im slightly confused. do you mean factory amp as in a separate amplifier or the amplifier that is in the cd player? either way, yes you can replace it. how do the speakers sound? if its making an annoying *scratchy* sound while it plays, you may have burned out the voice coils. in which case you'll want to get new speakers.