I have a RAID 0 w/ my 2 WD 80GBs in aluminum boxes. The Coolermaster 11s, to be exact. THey are in the 5.5 bays next to my CDRW. There's no air movement, and I ripped the fans out of the Coolermaster 11s to get rid of the noise. But the box is a giant aluminum heatsink. It gets warm... but it's not too bad. Probably warmer than the drive would be by itself.... But quieter, because it's muffled.
Anyways, it's been widely proven that the Zalman solution doesn't lower temps at all. It doesn't really change them. But it IS quiet. Something about no vibrations or something?