Since you have no choice but to go with an external box, the decision is how much and what to spend your money on. The Griffin iMike is a good option for audio only. I do this all the time with My Canopus ADVC series video digitizer: http://www.canopus.com/products/ADVC110/index.php It is compatible with the software already on your Mac and gives you the option of importing video as well as audio only, which may ultimately be a better investment even though it's more expensive. MOTO offers a great little digitizer, but it requires you to use ProTools. Fortunately, Garage Band allows you to minimize a lot of the noise artifacts that are inherent in analogue tape recordings and introduced in the D/A conversion and by the Mac itself. My old cassette tapes have actually never sounded better. The same is true for my old vinyl recordings. But as Charlieman points out, it is a time consuming business that requires constant monitoring. One pop or click and it's back to square one.