i've got an iMac sitting doing nothing. What do I need to do to convert it to my main music computer using Garageband 3 to compose and hold a 10,000+ iTunes library? I only intend to use it for that but I presume I need new OS, more memory, more hubs, separate CD burner etc.....can it be done? is it worth it? already got a mac mini but that's the family machine.