I have 5" mufflers, 3.5 staggered, single wall on my '13 WRX hatch for all most 2 months now. The sound has soften a bit and is very easy to live with after a thousand miles on. I don't even worry about the Po Po anymore in mixed city traffic as it doesn't really make so much noise they would stop me. Just did a 500 mile trip this weekend using the cruise most of the time at 70 mph and I enjoyed the stereo without any drone from the exhaust.
My 52 year old wife loves the sound and drives the car whenever we are out together. She wants the car next year once I go for my next new car. I said I can change the exhaust out for you if you take it, she said don't you dare! That is the best thing I love about the car. Women