I have the last of the G5 iMacs (2.1GHz, iSight). There are two firewire ports on the back: does that mean two channels or simply one with two ports? Same with USB. Are these separate channels or is it like a hub? I use four external drives (Firewire/USB 2.0) and want to optimize for video editing but really don't have much information as to how this machine is designed. If you really know the answer, please let me know.