I just purchased my first WRX last tuesday (July 5th). I just got out of a VW GTI. The GTI, although it is a great car, doesn't even compare to the WRX for many reasons but I won't get into all that now.
Your thread makes a lot of sense. I asked if the Subaru dealership could upgrade my brakes to the Brembos. Needless to say, I didn't get them and I am glad I didn't.
That being said, stopping distance also depends on the weight of a car. In an "Oh Hsit!"situation, you are correct in that nothing is going to bring a car to a sudden halt. However, good brakes, tires and weight of a car is going to make all the difference in the world if inches matter.
Let's say my base WRX Limited with its stock brakes and tires needs to come to a halt because I'm distracted with my iPod and I am coming up on a red light where other cars in front of me have stopped. I hit the brakes and I stop two inches from the car in front of me.
Let's say now that I have upgraded my car with various different things which has increased the weight of the car by some 300-400 lbs. Same scenario as above. I have to stop rapidly. I guarantee you that I will hit the car in front of me. Now, I suspect that even brembos wouldn't help me.
I am merely suggesting here that weight is indeed a large factor