20 inch pounds seems high, 12 would be closer to what I'd shoot for. Normally you expect a higher preload with new bearings than simply reassembling with old bearings, but that just seems like a little more shim would have been what it would have wanted.
I run 140wt in my rear w/lunchbox, but 85w-90 in open diffs. I am inside things too often to spend the extra on synth.
I agree with Bill, drive it for a week or so. If it get's worse, yank it, if it doesn't it'll probably just wear in and be fine.
If it was a 35 year old FJ40 you'd probably never even notice any new sounds :-)