Lets take a moment to talk about the audio outs.
The Mix Outputs function one way for the K2000 and K2500, and another way for the K2600. But all audio signals come out of the Mix pair, until you physically plug a cable into a separate out. At that point, any signal routed to that out is removed from the Mix and comes out of that particular out. So if you plug cables into all of the separate outs, there will be no signal coming from the Mix outs. But the effects actually only come out of the MIX outs.