If this problem only became noticable right after you changed the centre bearing I would almost have to think its something you did.But that is not certain. At a minumin I would recheck your marks on the two piece drive shaft to make sure you assembled it identically. If not and you express the possibility it might be so you may be out of fundemental balance on that shaft. Coincidence of course is another possibility or perhaps if you have done some other work on the car? The reason I feel this way is your description is really good but that particular complaint seems rare to me.In my again limited experience the resonance seems to fade out in the same area it originates in like a bad tire at a certain speed after you pass through the critical speed usually. You also seem to be describing a self dampening resonance as well to some extent. That is not quite so common in my limited experience. Perhaps someone else will clarify the issue better. As the resonance dampens it might seem to travel as well. Indeed it may be actually travelling. Also you might want to have a really close look at your rubber driveshaft flex disks. That centre universal was checked and found to be good when you had the driveshaft off? Still can be checked on the car if not.