I will note that buying this does make you eligible for a boost from 5 to 20GB in Amazons cloud drive thingy for a year. So a pretty cheap way to play with that.
Also probably worth noting - when you do a Amazon MP3 DL (which has NO DRM), you get it as a one-shot deal download.
Once it does your that one download, that's it.
So if you put music on your HDD to start, you might want to also back it up somewhere, as well - like on CD, another HDD, or The Amazon Cloud.
So if you put music on The Amazon Cloud to start, you might want to put it on your HDD and/or back it up also to CD.
You can upload whatever music you wish to The Amazon Cloud - even music you didn't buy from Amazon.
You can also re-download stuff that you throw onto the Amazon Cloud.
The Cloud could be considered another back-up for you, basically.
More info on
Amazon Cloud and MP3 Store. here.