The pre-tensioner pulley: suspect #2
After testing the belt noise and isolating it to the serpentine/drive/accessory belt, I began hand-spinning all the pulleys to check for bearing noise and movement. While I wasn't able to make the pulleys spin fast enough by doing so, I did manage to find some abnormally loose/wiggly pulleys.
Remember If you can feel it but not see the movement it's probably o.k. (only a few thousandths of an inch), however if you can SEE the movement; it's probably f*ed.