"closest 3 within 20 miles". (Or reorganize it about that limit) Who's going to drive more than that just to get to a dealer?distince is relative. When I lived in Corpus Christi, it was "forever" to drive anywere that was over 15 miles away. Now that I live in a large city, I think nothing about driving someplace that's 40 miles away(Fry's Electronics comes to mind).
I'd say just list the closest 3 or 5, regardless of how far they actually are.