External Case Cooling

if you already have a house fan then this may be the ideal solution.

No, you didn't read too closely. The problem is with a small external case (Startech Esatcase2). which has no sides, only a small vent in the back where the fan is. I have considered cutting a hole in the side, to place another small fan that I have, which would be more silent and move more air, but since I have never seen any kind of cowling available, that would make the fan look integral to the case, and I am not sure that the circulation would suffice, due to blockage by the hard drives, I'm looking for a better idea.