Storing Audio, video, and PDFs offsite for Ecommerce

We will have up to 300GB+ of files consisting of audio, video, PDFs, etc. that we will sell to our customers. Is there a way we can store these 100s of Gigs of files on Rackspace or another storage location outside of our web hosting but still be able to control permissions to the downloadable files?

What we are trying to avoid is someone getting a download link to an audio file and then simply being able to send that email+link to a friend. We want people to have to login with their membership credentials to our WordPress site to be able to download files from Rackspace, Box, etc.

Thank you!