You can go USB out to another source like an amp and it will use the Onkyo DAC but if it has its own DAC it may bypass the onkyo AMP and DAC. What are you going to use as an AMP?
Most likely the schiit Valhalla 2 which from what I've seen most amps only have rca, or xlr in not usb (digital) I'd have to go with a external DAC as well? Didn't really want to go that route being the Onkyo has decent DAC's (from what I've read)