wouldn't suprise me if the Hiper is louder. From what I heard, the Spoon N1 is the loudest you can get, and that the Skunk2 Mega Power (RS*R N1) is louder than an Apexi N1. Which I can vouch for, I heard an N1 on my car and then when I put the RS*R on, it was noticably louder.
-Andrew