Oh cool I've been waiting for someone to try this out and confirm if it works since I only use plughw with xbmc stand alone.
So lets clear this up. From your other post your hdmi device is hw:1,7
You used the following probe_mask in /etc/modprobe.d/sound.conf
options snd-hda-intel probe_mask=0x102
Now you have audio over your hdmi connection without making any other modifications? eg. asound.conf default.pa
Now onto your issue.
With your system you have 2 hdmi displays? What do you mean you get sound on the tv vs sound on the desktop? Can you elaborate more please I don't think I fully understand. Give me a complete physical description of the setup and issue.
I think I know what you mean now. The talk about TV vs desktop confused me. Try:
in the default.pa file
load-module module-alsa-sink device=hdmi:NVidia