Intel-hda sound drivers are a morass with manufacutures hard wiring the chip in different ways. Using alsa in linux one often has to modify the sound module. Examples are
here. I found a linux user with same model of motherboard who had success by using the
6stack-dig option. OpenBSD tries to accomodate the variations automatically.
The necessary xfce gstreamer plugins are described
here.
Do you get sound from the headphone jack?
Also, have you looked at the
xfce-mixer. Does what shows up correlate with the mixerctl settings?