Just so you know, from apple.com:
Fire Wire can work with up to 63 devices on a bus. The number of bus-powered devices you can connect depends on the amount of power available from the computer, and the amount of power required by each device.
...and if the devices are designed according to the FireWire standard, they can be turned on and off as needed. For example, all devices don't need to be powered on to use the last device in the chain. For the best result, and to avoid overstressing the FireWire port, connect one FireWire device to the Macintosh, then add one device at a time to the chain. Avoid plugging in live power adapters into devices connected to the chain.
I chain 4 devices off my mini w/ no problem.