https://bugs.freedesktop.org/show_bug.cgi?id=72087
--- Comment #3 from pyrodex pyrodex@gmail.com --- Thanks for the feedback Andy.
The Denon and the Panasonic are both in "Extended (0-255)" and it seems in the upcoming XBMC release you can adjust the levels. By default XBMC was set to 0-255 and I noticed the VERY dark scenes and settings so they suggesting changing XBMC to 16-235. Before I know about the XBMC setting I changed the Denon to 16-235 and it fixed the darkness issue. I have these same two machines with IDENTICAL hardware, etc. but the second unit which is upstairs in my Bedroom is attached to an LG 32" LCD TV and has the same issue. The ONLY common point between the two setups is a Griffin HDMI detective to prevent issues I've seen in the past when I shut off the TVs(and AVR) and leave the units running. The only thing I've changed in this equation was the leap to Linux from Windows with the OSS drivers for radeon.
FYI I used "xrandr --output HDMI-0 --set dither On" in my startup script after X started.
Any recommendations is welcome.