Honestly why do that!? Modifying the exhaust totally changes thr AMG sound. I've seen videos of X / h pipe modded 5.5's and they sound like the 645ci I had which had the resonator and X pipe fitted. Sounded ok and loud but higher pitched and raspy. Totally not the sound of an AMG muscle car.
Have you heard your car being driven from thr outside eg at a car wash? Get a friend to drive it around a car park for you. My e63 is loud already at town speeds and really loud at high revs.