Aftermarket head unit likely won’t play nice with OE style speakers with attached amplifiers.
Unless you’re good at reading electrical diagrams and already understand the basics of safe 12v wiring, as well as some if the intricacies of how stereo system components work together, my suggestion would be to call Crutchfield and tell them what your vehicle is and what your need, goals and price range are and then simply go with their suggestions and use their awesome tech support for help with the installation. If you follow this simple advice, I predict that you will be more pleased with the results that you obtain with less trouble and less risk of burning your vehicle down.
While I do NOT work for Crutchfield in any capacity whatsoever, my experience upgrading various vehicle sound systems over the years have proven to me that really do have excellent technical support, vehicle fitment guides and your purchases and satisfaction are backed by a no BS 60 day “no questions asked” money back guarantee.