@Hedgehog > The DJM-2000 is able to do this already. ;)
You can set it to have 8 Channel Outputs and 0 Channel Inputs, or you can set it up to record by using 6 Channel Outputs and 2 Channel Inputs.
Please check Pulse's video HERE.
Also just to mention, the DJM-350 doesn't have a built in sound card.