What worries me about using the H9000 as a DAC is that the big knob I assume its used as volume (when you allow for it) and it's not a physical fixed dedicated volume control so changes in software could make it ignore it or reset it somehow and blow up your eardrums. So I think for safety I would still route it throught a physical knob.

I agree, it's not a bad idea to have an analog volume control.  Of course, we will do our utmost to make the digital controls reliable.