It looks like some of what I need is here. What I don't see is how to either add an amp to the stock system or replace the stock amp with one that can power all 6 speakers properly.

I think I can pay someone to install a new head unit, with harness, etc.

I feel like Im making this harder than I need to. I am trying not to pay an arm and a leg to some shop that really doesn't know what they are doing, to install a head unit. If I have to tell them, I may as well do it myself.