Time to introduce you to my lastest project. I've named it "Silent Freak - The HDD mod." Aim of the project was to make all my noisy HDD's silent! And kept them cool enough so they still work ok. After thinking about many different ideas. Originally I wanted to do the complete mod within the pc case. But I knew I would never be able to accomplish everything I wanted. I finally settled on this basic (big box with small airflow) design... You may also remember the watercooled HDD in my other system, as part of my last project "SilverSilence". However this system is completely air cooled and very quiet! CPU fan is 80mm papst on 5 volts with this amazing Heatsink. 150 Watt they claim. It is an awesome quiet setup. Seasonic PSU has been modded with this fan running on 5 volts. Also 1 Papst case fan also on 5 volts. Together with my HHD mod. This is basically as quiet as "SilverSilence" (my watercooled setup), and is completely air cooled.
Now to the HDD box.
Finished HHD box
- happy snap
Bare insides. Thick wood and foam is what this mod is all about
. Also you will see a Papst 80mm fan attached to the lid of the box. 
Notice 3 small holes (13mm) where the cold air blows into the box.
HHD frame. Allows 2 hard drives to sit inside a box with maxium airflow around them. Rubber supports under the hard drives to stop any viabration.
Inside picture. You will also notice a baffle to stop sound traveling stright outside the small holes at the front.
Another inside pix. On the side you can see a hole cuttout where all the cables get pushed though.
Small hole is cut in the door my case. Rubber is fixed around the sharp edges.
Installed picture of the insides. Foam has also been added under the wooden frames to help with viabration.
Finished installed picture. The best thing is I can't hear the hard drives!!! btw The lid is a very tight fit and designed with 2 pieces of wood. The piece of wood with the foam on it fits inside the box. The other piece sits ontop of the box.
So far the hard drives seem to be 100% stable. They also seem to stay quite cool. Of the 3, the highest temp recorded so far was 50 degress under load (80mm papst fan was running at about 4.5 volts
. It's now running at about 6 volts ). Although that temp is not bad considering I've seen hard drives reach there max allowed temp of 55 degress inside a warm case. As long as all three hard drives stay under 50 degress, i'm happy. But at this stage i'm still testing it. So far this mod has been a complete sucess! Long live Silence! I will just have to keep my eye on the hard drive temps.
, you could easily fit this inside a case with <40degC temps... I'm glad your HDs are quiet, but that HD box is half the size of your PC case, and probably weighs just as much.