Hi radridd,
You might want to double-check the manuals for each receiver since I don't know off the top of my head, but what you're basically looking for, I think, is HDMI Pass-Through. Basically, when the AVR is in "Standby", whatever the last HDMI input selected was is the HDMI port used for HDMI pass-through.
So HDMI from both your HD-DVR and BD Player into your AVR, and a single HDMI to your XBR6. You would no longer need the S/PDIF cables.
A lot of the newer AVR's support this feature. I just looked at the Yamaha RX-V465 manual and it states that HDMI pass-through while the unit is in "Standby" only consumes 3W. Hopefully someone with a Yamaha RXV1900 or Onkyo 876 will chime in for more details.
Cheers,
Kermee