Trying to get perfect 2 channel audio with XBMC Eden

I'm having trouble getting perfect 2 channel audio with my XBMC (openelec 2.0 based) setup. I'm using my box's HDMI output to connect to a Pioneer receiver via a custom audio setting hw:0,3

root ~ # aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Generic [HD-Audio Generic], device 3: HDMI 0 [HDMI 0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: SB [HDA ATI SB], device 0: ALC888 Analog [ALC888 Analog]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: SB [HDA ATI SB], device 1: ALC888 Digital [ALC888 Digital]
Subdevices: 1/1
Subdevice #0: subdevice #0

I'm not sure what sampling rate the audio is at when it hits the PC, but there is subtle noise on some tracks and distortion in places which cannot be heard elsewhere. How do I get pure 2 channel / PCM audio? Why can't I just get direct passthrough from XBMC to my receiver for 2 channel audio? It seems something is being mucked with.

Thanks -

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Foxconn nt-a3700
AMD E450
AMD Radeon HD 6320
Openelec 2.0.0
XBMC Eden 11