Well, if you're going to do it yourself, follow my directions I gave earlier. But atleast try and get your money back for the amp install, as new wires will cost you a bit. A 4 gauge wiring "kit" will cost you probally $70-90. That will include most everything of what you need. But personally, I'd buy each piece individually so you get what you want.

Plus, of you teach yourself about your car stereo, you'll learn how to adjust it and remove it if neccessay, and you'll feel good that you installed part of it.