I have a rMBP (500gb) and an external 1TB drive for Time Machine backups. I keep my music (137gb) on my external HD so it doesnt take up tons of room on my actual MBP. Downside is that when I am away from my desk I have no music on my laptop. With my pics, docs, vids and general system files I have 283gb free...would you just move the music to the MBP and be done with it? What would you do?