Later this summer I sureley will buy a 4x10 cab to co-operate with my 2x10. I have been told that the 4x10 cab will be way louder than the 2x10. (Both cabs are Yamahas new ones rated at 4 ohms). But how can it be louder? They get exacly the same ammount of power - They should be equal? Tell me how this works. Thank you.