I'm going to start recording music on my Macbook using garageband. I need to buy a keyboard, mic and audio interface. I was thinking about this interface: http://www.rolandus.com/products/productdetails.aspx?ObjectId=702&ParentId=114 Let me know what you think, and I need suggestions for mic and keyboard. How many channels do I need for a mic, guitar and keyboard? I assume stereo is two channels per instrument. Also, what do I need to mix tracks and blend multiple tracks(including songs I already own) together?