i believe the 519 doesn’t suffer from bit loss that some earlier digital volume controls suffered.They still do, Thorsten Losche of AMR did research into this, and he says digital domain volume controls, no matter what the dac or player it will still "bit strip".
If you go direct (without the Jadis), are you at or above 75% for normal level, if yes go direct. (sell the Jadis)
If below go full up with the 519 and use your Jadis to set the loudest level you want to listen to, then use the 519’s volume control to reduce it when you need to.
Cheers George