Asus has been making some pretty great enthusiast computer audio products for the last few years. The Xonar and Essence lines have given fantastic quality and features for very reasonable prices. It appears that a new internal sound card is coming to claim the throne, which is great news as they company has been concentrating external products lately, especially on the high end.
i have a problem with my ASUS Xonar D2X and DMIX. It is not possible for me to change the "defaults.pcm.dmix.format" in /usr/share/alsa my audio/video/youtube files are always playing with "format: S32_LE" (defaults.pcm.dmix.rate is working fine). On my other rig with an Onboard Realtek Soundcard i dont have this problem. Iam also using on a extern DAC.