Clunk at stops
I have all kinds of clunks and rattles and my car only has 25k miles. Every GM car I've ever known makes noise. I just turn the radio up 
The jack sounds like a likely candidate.
Just to rule it out man...
Just to note though,I have a similar clunk.Kinda happens when shifting at lower RPMs..Especially 1st to 2nd shift.Sounds like there is slack being taken up in the driveline somewhere between tranny and differential.
I haven't checked my tranny mount though..("to do list").
I have had this on ALL of my F-Bodies..3 A4s and my current M6.On the A4s it would happen especially if you were accellerating and just suddenly let off the throttle..New tranny mounts worked in curing the sound on two of them but one of them was sold before I swapped it out and like said,I haven't inspected the one on my current M6.
Good luck...

