[Rubbernuts]

So I tried all of your steps above and at this step:

"Press F6: and you will be prompted with a selection window. In my example i have device 0 "HDA Intel" and device 1 "HDA NVidia". Select the second option and you will now see that you probably only have one option. This option is probably the 'S/PDIF' and it most likely will have a 'MM'. I just installed Eden 11 yesterday on a fresh install and mine was muted out of the box. Good chance yours is as well.
"
I can't unmute the 0,3 HDMI S/PDIF portion for some reason?

My aplay -l:

**** List of PLAYBACK Hardware Devices ****
card 0: Intel [HDA Intel], device 0: ALC662 rev1 Analog [ALC662 rev1 Analog]
Subdevices: 0/1
Subdevice #0: subdevice #0
card 0: Intel [HDA Intel], device 1: ALC662 rev1 Digital [ALC662 rev1 Digital]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: NVidia [HDA NVidia], device 3: HDMI 0 [HDMI 0]
Subdevices: 1/1
Subdevice #0: subdevice #0

So my XBMCbuntu is configured to use CUSTOM for both output/passthrough and with PLUGHW:1,3.

My setup is Acer Revo 3700->HDMI -> TV -> receiver

Good Morning,

In your above quote, I bolded two statements. You are trying to unmute 0,3 but your HDMI sound is clearly stated as 1,3 in your aplay.
If you forget about the receiver for now, can you get HDMI sound working directly to the TV Speakers by using Custom PLUGHW:1,3?