Well, I am alredy using a Clarion unit, but I bought a harness that has a little rectangular black box, which I think, retains the factory amp (am I correct?). On it, it has 4 little holes, where you can make some kinda adjustments. Now, if I get the factory amp bypass harness (It'll be much better with the HU power, correct?), do I have to do any major rewiring? Or will it just be as simple as installing all the other harnesses?