I had the harness put in when I did the head unit. I really think my next move is to replace the amp and maybe replace the sub in the rear, but try keeping the existing speakers.

My biggest gripe is I can't get it adjusted to hear the door speakers unless I really crank it up. At which point it sounds ok, but I can't play it that loud on a regular basis. And when I say ok, I mean just ok. The factory amp really pushes too much of the sound to the dash speaker. I have actually thought about just disconnecting that speaker to see how that would sound. I think the head unit I got is pretty good. It was a closeout for something that costs over $1,000 that I got for around $600 installed.