You can hook an amp to the stock unit. But you need to buy an adapter that will allow for rca jacks. I think it's called a high to low output. Most stereo stores sell them for about $25.00. You will also need the low voltage output adapter so your stereo can turn on the amp. also about $25.00. They both come with directions on how to install them to your stock unit.
I'm looking into the same set up.
I'm looking into the same set up.