Sort by newest post option

[Crippy]

Is there any way to set it up so that a new post in an old thread would move it to the top?  I already have it set to this display option, but it only works on new topics, and not on new posts in an existing thread

[ADMIN]

I don't think I can make it move postings up when they get replies, but I CAN add a box that shows the latest X postings, including comments and replies. Trying to figure out where to put this box; I think I can allow users to turn it on and off too. It's added to my punch list for scoop, and may or may not get done before we leave for Seattle for the wind seminar.
CHeers
DANF