Some configurations that will definitely work:
Get a headphone amp, connect it’s analog inputs to the DS’s analog outputs (either balanced or unbalanced), connect the headphones to the headphone amp, connect the amp to the other DS analog outputs OR, if the headphone amp has an analog output, you probably will be fine connecting your amp to the headphone amp’s analog outputs. Things will work and you won’t hurt anything by using both of the DS’s analog outputs at the same time: The warning about using both of the DS’s analog outputs at the same time is that you might (or might not) get some noise in the outputs from unbalancing the balanced output a little and you might (or might not) get a slightly raised or lowered top end if the cables are too long. For most systems these effects are not noticeable nor significant.
Get a preamp which has a headphone output, connect the DS’s analog outputs to one of the preamps analog inputs, connect both the headphones and the amp to the preamp.
Custom adapters/interconnects can be built to hook either the balanced or unbalanced output of the DS to the headphones or the cable that came with the headphones. Whether this would give the volume/clarity that you want in the headphones isn’t clear so you may end up using one of the above solutions anyway. Not the recommended path for someone who doesn’t already know how to wire the DS’s outputs to headphones.