Surround-sound audio cards can only be used if the outputs are true "assignable" outputs. In most cases, these types of cards are only used with software that can read and playback surround encoded audio files. The surround playback software "automatically" knows which channels to route the audio to. Traktor is NOT surround capable software. So in order for Traktor to be able to use surround-sound devices, the audio drivers need to allow for each output to be selected and assigned as a seperate output via normal MME/Directsound/ASIO Drivers. You should contact your sound-card manufacture to find out whether it can be used as a multi-channel assignable output card.