Head unit is abit too much work as the headunit runs most of the car's electronics, you can check out Tesla style headunit swap that some people are doing now.
I currently run Hertz HSK165 for fronts, HSK163 for rears with Audison Lrx 4.1k and 2x Hertz HX300D with Audison Lrx 1.1k. They all go through Audison Bit Ten processor.