Up to this point we couldn't find a true fix for that (crappy Realtek software).
One possible fix that nobody tried yet is try to change the default settings in the registry or some .ini file. Notice that if you choose, in the audio manager, to set your outputs to "5.1 surround sound", next time you reboot the "5.1 surround sound" will still be there. It might be possible to change the output configuration of the option in that combo box so that they will stick.
Kind of confusing.. I hope you got the idea.
Thanks to Joseph-yellow-duck-avatar for the idea.