(4) 8" Comp VRs = .0856m
(2) 12" Comp VRs = .10642m
8" Comp VR = 8.5mm xmax
12" Comp VR = 11.5mm xmax
The 12s would most likely be a bit louder but 4 8" Comp VRs would be pretty unique...not just your usual 4 RE 8s! Although I'm thinking 4 RE 8s would most likely be louder and about the same price, perhaps cheaper depending where you shop. So go ahead, be a rebel and choose an 8" sub rather than the RE 8 if ya want(even if it's better than the Comp VR)!