Today I got my new sound card, a Asus Essence STX II. After plugin it in and booting my Linux machine, the card was recognized by lspci as audio controller, but not listed by alsa as soundcard. Information on support for this new card under linux are hard to find. Due to the hardware similarities between STX and STX II, I tried to modify the existing STX driver in order to work for the STX II too. And it seems to work quiet well: I have sound, can change the volumes, switch between speaker/headphone/frontpanel, enable the mic boost etc. I don't have the H6 childboard for surround sound, so I can't test that. I tested my patch [1] with a 3.15.8 kernel under Arch Linux.
Just wanted to share this information for others to get it quickly working, or maybe even include it after a review from the devs.