Rodecatser pro 2 with external DAC ?

Hi everyone. You might here this question a lot but with different configuration. Question for those who know the possibility of have DAC connecting to Rodecaster pro 2 to have better headphone experience while controlling the volume through the RCP2 ? I have Monolith thx DAC/AMP running my HD 800s . Is there anyway where i can have the sound coming out from my RCP2 but being processing by the Monolith before it get to my headphone ?

Thank you in advance