Griffin Technology: "Adapter and Amplifier for Apple Pro Speakers"
Provides 18 Watts to drive Apple Pro speakers (Harmon Kardon). I need to look at those speakers. I don't think they work with the G5 iMac. This won't work with most PC firewire laptop adapters -- they don't provide enough power. Might work with an iBook. I'd worry about burning the firewire bus.