Very exciting, thank you for the update and your continued efforts to support this line of cards.
I would like to chime in and say I have an Asus Xonar Essence ST -- that is, the more recent PCI version of the STX (which is PCIe) and would love to see OSS support for this as well.
In particular, ALSA seems to have no end of trouble with SPDIF (IEC958) support. That is to say, it works fine, up until it mysteriously stops working while in a state of sound transition (typically while jogging music or video, or between songs). It would be lovely to have an alternative that supported both the on-board DAC as well as the SPDIF out as I sometimes have need to use an outboard DAC but mostly intend to listen directly from the headphones out (as soon as kernel 2.6.33 goes final; I tested rc2 successfully earlier today).