Not sure what you're referring to by DLC, but you'll find fan-created content in the Downloads section of this site.
Similarly, for the "Powers book" if you're referring to the Powers section of the HERO System rule book(s), that's one of HD's main purposes (i.e. all included). If you're referring to the UNTIL Superpowers Database or similar supplements, you can purchase downloadable "character packs" for HD which include the various Powers and builds from the related books, typically as prefabs for HD (or you can just enter those on your own).