One thing you don't want to do is mount two of these drives in adjacent barckets so the drives almost touch, especially without a fan. They will get very hot, and this is not good. I am talking about "too hot to touch with the bare hand" hot!
On my system, I ended up rigging some brackets so that the lower drive hangs about 1" below the upper drive, and then I rigged a little fan I removed from a Pentium-1 heatsink so it would blow between the two drives. Things got a LOT cooler.
Or, use dedicated HD heat sinks, if you can find one that it quiet enough.
I just picked up a Seagate Cheetah 10,000 RPM drive. It should be interesting to see how hot it runs!