Matthew van Eerde wrote:
Can you hear system alerts when S/PDIF is the default?

Yes.

Although with the X-Fi, the global format for the "Spdif-output" is set to "16 bit, 44100kHz" by default which my decoder apparently doesn't support since the sound gets sped up. Setting the format to "16 bit, 48000kHz" fixes it.

EDIT: Just to be clear, everything works normally with the SPDIF output, except actual AC3 or DTS passthrough, which only works in the audio control panel (by using the test option) and in Media Center, but not anywhere else.