CQ output (stereo link) to headphones (stereo link) would be great if possible.
For example, when Stereo Link is enabled for Out3-4, the source of the headphone output will automatically become a stereo pair and you can listen to Out3-4.
In this case, it would be easier to use if there is a Mono button to listen to 3+4 in case Mono is needed as a source for headphones.