Agreed with everyone on the sound, but I think the S55 sounds much better with a simple midpipe. Check out this F80 M3 with an Active Autowerke midpipe and an otherwise stock exhaust. I know this is an M3, but I'm hopeful that we can get something similar for the M2C.
I think it sounds much, much better than the raspy lawnmower stock S55 sound. According to Active Autowerke's dyno, it also added 18 WHP and 30 LB FT of torque and shaved off a few pounds. I think part of the gain is because M3 and M4 S55 applications have secondary cats (AFTER the O2 sensor, so no CEL issue
) that the midpipe eliminates. I'm assuming the M2C will have the same.
You can probably have a custom muffler shop make something similar if you want to save some money, too.
Seems like the perfect first mod because it checks off multiple boxes: Add 18 horsepower/30 lb-ft, make the car sound great, and lose a few pounds.