Cassettes to digital
I think folks make things more complicated than they need to be. I still have a quality cassette deck and use it to transfer tapes into the computer, using a very good little downloadable media program called Jetaudio. Converting the music to whichever format desired is easy enough after it is in the computer. The tape deck is simply plugged into the 'in' jack on the sound-card. I've done the same thing with my records and record-player. Good luck.