I have a large collection of music stored on an Archos Gmini X202s mp3 player stored at /media/disk20G/music/[Artist]/[Album]/[title].mp3

I have a smaller collection on my PC stored at ~/music/[Artist]/[Album]/[title].mp3

I use my PC to rip new music and then put it onto the player using cp. I also but music on from other PCs depending on where I am at the time.

I want to know will running

rsync -avh ~/music/ /media/disk20G/music/

save all my new music onto the player without affecting files that are already on both systems or files that are only on the player.

I have recently started using rsync for backups but in this case new files only occur on the system I'm backing up and not the backup location.

Is there any better programs for doing this task (I would like to stay on the CLI as much as possible)

Should work fine - I use rsync for the same purpose (though I use the options -ravou, out of habit). If you want to synchronise both ways, I think you'd need to run it again with the filepaths switched round (maybe as a little script). There is also Unison, which does operate both ways, but I can't really vouch for it (never used it).