Alan has over 100GB of music in his iTunes library. He's at the point where he's about to run out of space. Leo says first thing Alan should do is get iTunes Match. For $25 it'll let Alan upgrade his songs to the best possible quality. Once he's run iTunes Match, he should delete all the tracks that have successfully matched from his computer. Then, redownload the matched music.
Then Leo says to upload 25,000 songs to Google Music. Leo also recommends backing up to an external drive, just in case. If money isn't an object, Leo recommends getting Network Attached Storage (NAS). That has the benefit of having it stored and available in the house. Drobo has a new NAS called the Transporter which makes it available in the Cloud as well.