In that list is everything but the audio folder path, Open the Audio Data tab and you'll see the file path for audio.
Also I make sure and tick the COPY AUDIO WITH PROJECT box. when saving my files for the first time or as a SAVE AS.
The audio folder should always be inside the project folder.
I save each song in a folder. Those songs will also be in a Album folder or a "Original Song Ideas" folder.
I'm not sure how Dropbox will be for audio as I'm limited to 10 Gigs and I have at least 300 Gigs of Sonar files right now. They would be fine for CWP files with mostly MIDI tracks, but audio sucks up bandwith as Sonar is working with 32 BIt etc.