You will have no regrets with the Megan. I've had it on my car for 18mos. now with the Turner Test Pipes and the car sounds amazing. I have people follow me just to tell me how good the exhaust sounds. Fitment is good, no issues with broken brackets, keep in mind its pretty much just a rebadged Agency Power exhaust for a 1/3 of the price.
It is not the most aggressive of exhausts, more in line with the Akrapovic in that it isn't the loudest exhaust but still souds very nice and aggressive with the Test Pipes.
As far as stock with full OEM xpipe, it is more aggressive but definitely sounds like its been neutered.
2013 M3 Coupe-MR/BLK ZCP, identical to my 2011.
2011 M3 Coupe-MR/Blk
2007 Porsche 997C2S Speed Yellow/Blk sport seats
2004 BMW M3 Imola/Blk