I am looking to upgrade my sound system, but I need some direction. I don't want to replace the head unit, but I am willing to replace the speakers and/or factory amp. I want to be able to turn the volume up all the way without the sound getting distorted. I want to spend around $500 or less on parts, but if there is a lot of labor involved I might spend more to get it right. Please get me going on the right path and give me links to products when you can.