I'm glad to have found this thread. I've now duplicated the ringtones and songs I'd like available as alerts and notifications. As a result, I've deleted 3rd-party alarm clock I'd downloaded because the stock app could only use sounds in the "alert" folder.
However, I'm disappointed with the need for such a workaround. It'd be nice if the Epic could look to one sound/media folder for all ringtones/notifications/alerts.