I built a raised 3 rail loop so the grandkids can run their stuff. I figured someday I would add a subway set running around up there to add interest. Having the cars with the opening doors looks great to me. So I keep an eye open for a set that looks fairly modern, with the opening doors. Maybe an above ground NYC set or something that runs in Chicago? I can't decide. Whenever I look, there's only extra cars for sale, older sets, or the basic set without power doors.
Here's a glimpse of the raised track in the background.