Got the D back from the dealer today and it turns out that the 10-25mph flutter/chirp that varied frequency according to speed was a bad part in the drive shaft. Unfortunately I don't remember exactly what piece they said, but the solution was to replace the entire drive shaft. Seems to have done it for now. We'll see in the next few weeks. Just thought those of you with a similar problem would want to know.
On a side note, they said the brake grunt was normal and a lot of people have been complaining about it but there's nothing they can do. (Should I be satisfied with this answer?)
--Mike