the db rating is just how loud they will be. since ill have 4 of them i want each fan to be as quiet as possible. now the CFM rating will effect how well the fans cool my amp. its like, if its 90* and you have your ceiling fan on the lowest setting, it wont do much. but if you get that bitch to blow a lot of air, itll cool you down a lot better. now when we go to an amp rack, i have no idea how much CFM is needed to cool the amp. hell i dont even know if 30cfm is a lot or almost nothing.
now i could just go with the highest CFM rated fan i can find but they are louder. so if i can get away with less air movement and have silent fans ill be that much more happy.
i have been looking at those fans but i think i can get a better one. how many did you have? could you hear them?