This page is dedicated for Xonar hardware mods discussions.
If you wish to make a tutorial, I will publish it here with credits to the owner. You should submit your article at this e-mail address.
Also I will post any links that might be useful.
Articles and guides:
1) Xonar Essence STX Op Amp Upgrade by Adrian Tache.
2) Modding Xonar cards by Con.
3) Xonar ST/STX modding discussions on diyaudio.com forums.
4) Xonar DX modding discussions on head-fi.org forums.