Blue:
It's not much louder than stock. Infact, it's less loud on the freeway and off-throttle drone is almost non-existent. However, people have told me they can definitely hear me coming from down the street, versus before where you couldn't tell until I was almost infront of the house during that off-throttle engine braking.
One friendly tip when installing the MSCBE: there is a section where the two pipes slip together and are clamped tight. There is also a line marked on the pipe showing you where they should fit. If you line it up at the marker or over it, the exhaust will knock against the car during hard bumps. However, if you pull it too far away, the clamp won't seal and you'll have an exhaust leak. I do, and still have this issue where a tiny pinhole area right where the two pipes are joined is slowly puffing soot onto the outside of the exhaust piping.
When you install it, start the car and get underneath so you can hear if it leaks or not. We had it on a lift and we started the car, then lifted it back up while it was idling and kept noticing it and adjusting it until we could get there as close as possible. Unfortunately, it's still not fixed so we may try some copper gasket spray or buy a 2nd 3" clamp to put next to the first one.
But you will not regret the throaty Subie sound that comes from this exhaust. You will however, lose a smidge of low end torque, but the higher rpms climb quicker.