I just saw the youtube videos of your exhaust and they sound different on mine. Maybe it's the microphone, but on my car, as I release the gas pedal and the RPM goes down, the RPM bounces back up from ~1000 to ~1750. When that happens, my WRX mufflers make a sound that I can only describe as a boom from a sub-woofer.
Regardless, that drives me crazy as I do 90% city driving. As you've mentioned, the mufflers are quite at highway speeds, but I can't stand the sound at low RPMs. I've decided to put my stock mufflers back on.
By the way, you're car looks amazing. I'm quite jealous of how you've set the car to your likings. Cheers.