Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
Ever since ASUS first released its Xonar line-up of cards, I knew I had to have one. But, being that I use Linux as a primary OS, I knew that the chance of me finding good support was slim. Well, that support may have taken a couple of months in the beginning to come to fruition, but since then, the open-sourced ALSA drivers have come to support every Xonar model available, along with many of their specific features.
This past fall, I "upgraded" my Xonar D2X to an Essence STX (I use quotes because both cards are about equal in their awesomeness), and as I expected, the card worked just fine under Linux. One issue I did mention, though, was that the volume on the STX could reach levels impossible on the D2X... dangerous levels. Because this card is designed for headphones, it has a built-in amp, and I assumed the loudness was due to what was essentially the amp being set to max power by default.
Aside from that issue, though, the card offered an expected range of controls for both input and output, so all was well. Compared to Windows, I can't find a real fault with the Linux driver.