the best case cooling scheme, and thus best method of drive cooling, it to use the fans in the back and top of the case to blow air out of the case.
Then control how the air flows over the components you want cool.
On my case there's a 100mm fan in the top and a 150mm fan in the back both blowing out.
In addition there's a 150mm fan in the bottom of the PSU blowing out through
The PSU, the CPU cooler draws air off the CPU heat sink and directs the hot air towards the PSU fan.
The air inlets in my case all encourage airflow across the hard drives
And while I have one older WD 250gb drive that gets hot enough to
brand cattle when run in that drive bay none of my other "loose"
drives runs more than 3-4'C warmer than the internal drives
(that have their own air inlet) the internal drives in my computer
stay at 40'C
How hot do your drives really get?