Review: WiebeTech FireWire DriveDock and Super DriveDock: " USB's power rail is good for a flyweight half an amp at five volts - 2.5 watts. This pretty closely matches the needs of laptop hard drives; they all run from five volts natively, which is why they can work in single-wire external USB enclosures. But it's no good at all for running more demanding devices.
Full-spec FireWire can deliver serious voltage and hefty current. All the way to 40 volts at 1.5 amps, from the original spec. That's 60 watts, baby, and even after losses in DC-to-DC conversion to the 12 and 5 volt supplies that desktop drives use, it ought to be plenty to run two or three full sized drives. 3.5 inch hard drives, CD or DVD readers or writers; no problem."