Hard Disk Cooler

I wouldnt worry about it. The normal airflow going thru the case should be enough. The HD cooler will just add more noise to your case.

With all those case fans I think you have sufficient air flow to cool the drives. IMO it doesnt require much airflow to cool the drives significantly. I have only 1 case fan located in the front. My drives are mounted behind this and eventhough the fan has been reduced in speed (in order to reduce noise) the drive temperature was reduced by almost 10 degrees.

I suggest you measure the drive temperature with and without your case fans running.

<i><b>Engineering is the fine art of making what you want from things you can get</b></i>