How do I connect my guitar to my G4 iMac? It doesn't have an audio line-in/microphone port so I can't use the Monster instrument adapter or any of the cheaper alternatives. Is there an external device which contains an audio line-in port? I am a bit hacked off as I bought Garageband with the intention of recording guitar tracks on it, but I have to use it with the built-in mic, which is pretty crappy. Any ideas?