Diamond has strayed somewhat from the reference design provided by ESS in order to include a few unique features. Most prominent is an expansion port on the rear portion of the card to facilitate Diamond's upcoming RioPC daughter card. As more information surfaces about this add-on, we'll be sure to keep you informed.
The Canyon3D processor has the ability to output to 2, 4, 4.1 and 5.1 speaker setups. At the expense of the subwoofer output and analog center channel support, Diamond was able to add a dedicated microphone input. Since the microphone jack is shared with the line input on the ESS reference design, Diamond's modification will be a blessing for the majority but a curse for those few with 5.1 sound systems who won't get the dedicated LFE and center channel output.
Unfortunately, the MX400 comes with fewer internal connectivity options than the competition. Among the missing amenities are an S/PDIF interface for digital CD audio and a stereo AUX input for those with TV tuners (there is, however, a mono input for connecting a modem). An optical output would be nice to see for those with MD players or "high end" speakers, as optical connections are more widely used in audio components.