I am thinking about adding a CD-RW drive. In general, you are limited to just four IDE devices in a system. You can have only one master and one slave device on a channel, and you can only have a primary and a secondary channel.
Some devices can add a third channel, however, making it possible to add one or two more devices.
If you already have the money invested in IDE devices, adding a third IDE channel may make the most sense. If you are just starting to configure your system, however, it may make more sense to plan on using a SCSI bus. Submit a tip or question.