I'm using a Xonar D2 with a piece of test equipment that's very sensitive to the timing of a 5.1 audio signal. Unfortunately, the sound card is adding a delay to some of the channels (15ms for the surround speakers, 5ms for the center speaker), throwing off the calculations in my test equipment. The driver settings app offers only very basic controls to do this, and may even remix the sound, which would be a Bad Thing (TM).
I could adjust for the delays in the audio files that I'm using, but I don't want to do that because it would make them incompatible with other 5.1 sound equipment. Fixing the problem at the sound card level is the preferred approach.