some external HD manufacturers allow you to chain their external HD's. They'll have TWO firewire/usb ports on the back, one to send to the computer, one to link another HD. understanding that the macbook can supply power to one external HD, will it be able to supply enough power to a second chained HD? I dont imagine going any bigger than that. of course, I'll use it plugged it so it doesnt draw power from the battery, but im curious if the firewire/usb bus on the macbook can support naturally chained external HDs. thanks!