I've used litterally dozens of these cases, so I'm fairly familiar with them.
If you want to cool your hard drives, I would recommend finding the absolute THINNEST 60-80mm fan you can possibly find and mounting it directly in front of the hard drives. The sheet metal these has many evenly spaced holes that make it easy to put a fan on the inside of the case and secure it with screws from the outside. It may not fit 100% perfectly, but you should be able to get 2 or 3 screws to hold it.
The important thing is to remember THIN... there is only a small amount of clearance between the inside of the case and the hard drives. On other thing that can be done is to mount the fan on the outside of the sheet metal (but hidden under the front bezel) and secure it with screws from the inside. In either case, if you have a dremel tool or some other method for cutting away all of the metal directly in front of the fan, you will get better airflow.
On other thing that I regularly do is to drill out all of the holes/dimples that are part of the In-Win design at the very bottom front of the bezel. I'll usually mimick their design by making two sizes of holes but ending up with the smaller of the two sizes being bigger than the standard holes on the case. Again, this is to increase airflow. If you are going to be keeping this case on the floor, it's also a good thing to raise it up on top of something a few inches since all of its air is sucked in through the bottom front. If you don't, you can easily block access to new cool air for your case.
Good luck,
Joe
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