I'm upgrading my audio system soon & will be paying a professional at my dealership to install. He said if I buy everything, installation will be $150, assuming I keep my factory stereo. I dunno how much it will be to switch to an aftermarket HU, but should I keep factory or go aftermarket? Would I keep my sirius satellite if I upgraded? And also, on some HUs, theres an option to mute subwoofers (because most HUs have a dedicated sub pre-out). How would I do that if I kept my factory stereo, if I chose to? Thanks!