I've had heat issues on 4000 desktops with Flyers to the point that I've left the case off of them.
If you have a tower or no Flyer, it may not be an issue.
Depending on the cost you can afford, if you are using a Flyer, the Flyer SSD drives from DiscreetFX would be much smaller and cooler than a stack of old SCSI drives.
Using a CF drive instead of IDE would reduce the heat and improve the performance as well. The drives and the Toaster/Flyer are a lot of the heat.
Also, SSDs and CF drives are shock resistant.