Always had a shimmey that started at aprox. 63mph but now, in addition to that I'm getting a rough vibration. You can feel it in the floor through your feet, through the seat and in the shifter. It almost feels like a grinding from a bad bearing. Any suggestions on what to check first?

 

bent wheels? are your wheels factory originals?

 

How many miles on the tires? How long since you have had an alignment? Being that it is an 06, I am guessing that it is still under warranty and that it is the dealer's problem. Since you say that you have always had the problem, which I assume is since the car was new back in 2006, what does the dealer say in response to your complaints?