premium stereo

Hey guys, just had a quick question I have been trying to figure out. I currently have a 2019 Mustang with just the 4 inch radio in mine, and have been looking at salvaged vehicles for a OEM premium radio. My question is if I am to buy a used radio, is there any programming or anything needed to...

I've searched quite a bit, but haven't really found a definitive answer to this question: Does replacing the rear deck speakers with a two-way (i.e., Polk Audio DX651 or similar) actually make a difference with the stock head unit and EQ (GT premium 9 speaker system), without reprogramming the...