Thanks to Sard for letting me check out his AW E92 with the Akra system. Very classy car.
I found the sound to be comparable to stock in volume--no harsh noises anywhere in the rev range. It looks awesome, and there aren't many systems out there as light. If you want to get noticed from a few blocks away, this probably isn't the system for you. Gintani has that covered. If you want subtle function over volume and can afford it, the Akra is a great choice.