Reply to Car stereos

I have an absolute bitch of a time getting my mixes to translate well to car stereos - especially the cheap ones. They sound good enough everywhere else - head phones, stereos, computer speakers, my monitors (of course). To make matters worse, I don't own a car but I just got back from a road trip where I relistened to my "catalogue" on a rental (shitty ford focus factory stereo). The bass is just so damn exaggerated in a bad way where kick and bass just swallow the mix.

Now I know some of my mixes are too hot on the low end. Some of that is by design, sometimes it crosses the line into just sloppy. How worried about this should I be? Should I just ignore it and tell my self - shitty stereo sounds shitty? Some of other ppls tracks I listened to managed to sound half decent and some had the same problems mine do. I don't want to focus too much on getting it to sound good in these situations and lose the heavy low end in places where it needs it (NOT super exaggerated systems).