I use iTunes Match so all my music is in the cloud.
What it does is...
1. Matches your music against the iTunes DB.
2. For tracks that match, you get the full-on high quality version from Apple (yes, even if 'your' version is some rubbish quality rip or download)
3. For tracks that don't match, your track is uploaded into the cloud for you to access as and when.
£21.99 or something and you have your whole collection with you wherever you go. Massive bargain.
Is this an annual fee?