you can use those speakers, but you'll need an amplifier to power the speakers. griffin used to sell a couple things that would work: the powerwave was a USB audio interface (plug the box into USB, plug speakers into box), there were also other outputs available on that box. the iFire was a small firewire box that did the same thing, but only had one output, meant for the pro speakers.
so you can use those speakers, but you're going to have one of these things first, and i don't think griffin makes them anymore.
tr