I noticed this right from the start when I checked for hum. I also noticed it completly goes away if you switch sources until the volume is changed or a signal is applied. I was happy I didn't have any hum.
Maybe it's from the volume control IC. Since we hear it when the analog bypass is selected that rules out noise from the digital signal path(SPDIF,DSP,DAC).
Switching digital cables should never change a noise threshold anyway, it's digital.

I've never been able to see hiss on a scope. I used MC33284's in my filters(Burr-Brown rep never gave me any samples, jerk!) and they hiss quit a bit.
Overall my hiss is about the same as my old system. I can't hear it accross the room, only right next to the speaker.
It's more noise than I expected.