I think you can get a lot of the superbox content from their websitethough the superbox does come with some extra bonus content. At these prices though I would personally be buying the super box.
http://www.egosoft.com/download/x3tc/bonus_en.phpsteam said:Bonus content with installers for Egosoft and fan made add-ons. To access the bonus material, select Library --> Tools --> X-Superbox Bonus Material from your Steam client.
http://www.egosoft.com/download/x3ap/bonus_en.php
02.Jun.10 X³TC All In One Bonus Package (v4.1.01) 1.21 MB
Simply run the .exe and follow the instructions. Only the plugins you select will be installed.
General information about the X³ Terran Conflict Bonus Pack and the individual upgrades is in the overview topic for the Bonus Package.