Keep the setting on True Cinema........that is the closest to the THX mode. It is very hard to find optimal settings for your room ambiance since lighting changes from place to place and what settings might be applicable to me might not work for you. Which is why every tv set needs to be calibrated within the viewing room. However, let me share my calibrated settings and see how they work for you. I suggest to keep everything the same only the brightness could be adjusted to your liking.
Contrast 36
Brightness: 0
Colour: 30
Sharpness: 0
Vivid Color: Off
Eco mode On/Off
Intelligent Frame Creation Off
P-NR Off
Gamma 2.2
R-Gain: -1
G-Gain: -1
B-Gain: +6
R-Cutoff: 0
G-Cutoff: 0
B-Cutoff: +1