Digital Stream, Is it to soon to make the switch??

hello

Im planning on finishing my system with a new Majik DS,however i have had some serious concern around the reliablity of a nas etcc. My concern is that as i start aquiring music via download, whats to say my hard drive does not crash and i loose all the music ive downlaoded and payed for?? Do i need multiple storage for back up purposes?? Seems a bit of a pain in the ass! I know how good the Linn DS units are already but could use some ideas or suggestions to make the transition perhaps a little less stress ful.. Thanx J