Can you put in a thick runner in the hall with a thick pad?

We would definitely try that. We don't think that that will be enough. I found an earlier thread mentioning rc channel for the sheetrock and gypcrete, I just need to find out more about those options. If they're effective, they might be worth the cost,
Thanks

To stop sound you need to stop the transmission of vibrations, Stuff the joist spaces with batt insulation, attach sound bar to the bottom of the floor joists, then re-sheet with 5/8 drywall.

Thanks for the input Peter. I'm trying to find out more about the "sound bar": what exactly it is, how expensive it is, how much headroom I lose in living room below, and how effective it is. I understand that sound is subjective but given the expense, I'm not willing to undertake the expense without some confidence that it's worth it. I have seen mention of "floating" a floor as well.