1) ~700 MB a disc for 13 GB of MP3's? no thanks.

20 CDRs? £20 can't be beaten as a price point here, and it's not like you back the whole lot up every day.

2) I don't think so

IDE disc + removable caddy thing = not all that much money. If you're worried about the IDE disc itself not being reliable -- buy two! buy three! It's still cheaper than a DAT streamer.

3) some other media storage

I use a DAT streamer, on the basis that CDRs are fragile, DVD-RAMs have unknown ultra-long-term reliability, and Travan and VXA might disappear tomorrow. DAT is not disappearing anytime soon. Read the Digital Dark Ages chapter of The Clock Of The Long Now in order to get worried (it used to be available on http://www.longnow.org but doesn't seem to be there now).

Peter