Congrats on your new car! Welcome to the forum. Thank you for taking the time to type your wall of text in proper paragraph form. Makes wading through it MUCH easier.
As others (or maybe one?) said, enjoy the car stock for a minute. The WRX benefits from well planned suspension upgrades most of all. The brakes can be improved as well. Then you can have fun and bolt an exhaust on and tune 'er up. You'll be pleasantly surprised at how the suspension mods and Accessport or other tune transform the car.
Have fun!