A week ago I became owner of a 2010 base MKX. Far nicer than the jeep it replaced but less features than my wife's nicely appointed 2016 MKZ. I have no manuals and am learning this car. Radio has a 6 speaker system (so it appears) with a 6 inch in each door plus a tweeter in the front doors, adequate is a stretch. I don't know if there is an amp (no sub). Crutchfield in not particularly helpful, their site suggests 5 1/4 coaxial speakers and their online assist tells me bigger is better and a 6/8 coaxial is better. I am thinking a 6 inch woofer components with tweeter (maybe 6 1/2) would be a better choice. Being somewhat old school, I am thinking MTX or Alpine for an amp of approx 4 x 50 but I don't know what is current.