I have had this same question and not received a real response.
One suggestion is to use something like a Gefen HDMI Detective. When you have this between your HTPC and your AVR, the HTPC will always see the EDID of the AVR. This should solve your problem, but note that if you remote desktop into your PC or unplug any of the HDMI cables it will revert settings.
You might also try the new HTPC Player (link below). This player is a bit easier to go and change these settings back, and also seems to take effect immediately. I recall needing to restart the Windows Player to get the audio settings to actually take effect.
Good luck!
