I am not using the AVR's you mentioned, but I do have an Yahama RX v1900 and have HD Audio formats playing fine on the PowerDVD10. However, I did have to mess around abit with my grahic card drivers to get this to work. I didn't have to include and EDID overrides to get this work, as long as my AVR HDMI input passthrough was configured for Video only. If Video/TV is configured, then only LPCM 2.0 will be passed through to the AVR and Television.

I have an ASUS EAH5455 Silent (ATI HD 5450) grahic card. However, I had to use the RealTek HD ATI Drivers and not the ATI drivers to get the HD formats reconized by my AVR and PDVD. I have no experience with Nvidia. To get the formats working in PDVD the HD maternial needs to be playing first in PDVD before the HD audio settings will be selectable. You should have the choices of PCM, DTS/Dolby or HD Fomats. Not sure the exact messaging, but you will want to select the third choice. I do not have 3D capabilities.

I am also using three zones in my setup, but had to add a splitter and D2A converter to get this working, as my AVR only supports zone 2 and 3 as 2.0 from analog input. I spit the Toslink output to feed LPCM, DTS, or Dolby formats to the 2.0 analog connection...I select between HDMI and Toslink depending on what I am playing and where I need it directed to. There is a MC app on the net that proivdes the ability to select audio channels...not the best solution, but given the limiations MS has provided on audio default channels and AVR's limited downsampling of bitwise to additional analog zones, it works well...
Good luck.

I went ahead and went with the Denon AVR791 and in very short tests it seems to be working fine even the 3D pass through with HD Audio. I will try hitting it harder this weekend and see if i am still happy.