Bent wheels. At least that's what they told me.
Others have reported (very rare) this being caused by the hub &wheel bearing assembly (they are ~$140 each). Only way to determine this is drive car on lift or jack stands without wheels on.
I am in process of replacing everything short of brake rotors. I have all bushings replaced and will be putting in new ball joints this weekend if my 3' bar works.
Also consider a road force balance, as Subaru recommended that for the shimmy issues.
As for your shaking, are you a 5MT? My flywheel was busted (dual mass springs) and vibrated the car like mad for the 20k I drove it like that before I realized it was the culprit.
Last edited by compsurge; 06-01-2012 at 08:30 PM..