Not sure about what the part number is but I have been using the diagrams that are located here to figure out what the parts and such look like and what the cost of them are. This is the one for your car:
I checked the voltage again on mine and I am fairly certain that it is the blower motor that is bad. I get 11.5 VDC with the engine off a the connector when the fan is in the fastest position and the voltage decreases as I turn the dial down until I get to the Auto position at which it jumps back up to 11.5VDC again. I am going to try and take the motor out next when I get some time and try to jump it right to the motor to see if it comes on.
Does anyone have any information on removing a blower motor from an 06 STI? Any info or pictures would be good.