Any one know if any double din aftermarket stereo work with the subie or do I have to get a mounting bracket or certain size deck ??

 

Any Double DIN or Single DIN with pocket will work.

For your '09 Impreza, you will need a Metra 95-8902 Double DIN Installation Kit, Metra 70-7552 Radio Wiring Harness, and, if you have steering wheel controls, Metra Axxess ASWC-1 Universal Steering Wheel Control Interface.

There are other brands than Metra, Like Scosche, for example. I've used Scosche and Metra. I like Metra more.