I have always been an audio geek. There hasn't been one car that I have owned in my lifetime that wasn't stripped and redone to get rid of the horrible mess that manufacturers call audio. Here is now everything progressed since I bought the car in June of 2011.
The first thing I did was get rid of the stock head unit in favor of the Pioneer Premiere F90BT. Given that the 2011+ cars came with actual 2-way speakers in the doors, the aftermarket HU actually did a lot to prove sound. The factory HU has almost zero power to it and you can tell as soon as you pick one up. They weigh nothing.
The first speaker swap was for the Hertz 165XL 2 way components with passive crossovers. A friend of mine made and wrapped the a pillars to accept the tweeter and move the front stage forward in the car.
They were powered with a DLS RA30 3 way amp under the driver's seat.
That also went to a Dayton HF 10" subwoofer in an Audio Integrations box.
After messing with the F90BT for awhile, I didn't really like the overall look in the car. I got rid the F90BT head unit in favor of the Pioneer X930BT. It was the head unit that most resembled the interior and had the best functions at the time. Ironically enough, Subaru thought so too and the Canada spec WRX's and STI's got this head unit as the factory option for navigation.
I then swapped out the DLS RA30 for the new (at the time) Hertz HDP4 4 way amp for more power on a smaller footprint.
The additional power to the sub started heating the voice coil of the Dayton, so I switched that out for a JL Audio 10" W3v2.