[JohnM]

You are a bit scuppered, unfortunately, unless you can use the on-board audio. Apple's Java virtual machine doesn't provide any access to audio inputs other than the on-board input and gets very upset if you try 48k instead of 44.1k. Leopard has, i'm told, sorted out at least the inability to access other audio input devices but I don't know whether it solves the 48k problem. There are also a range of rendering and component size problems under OS X with the current build of REW, but I have sorted those out in the next build which is being beta tested at the moment.