Have you tried using settings on AVS posted by other owners of the 550?

I have done this for both my LCD and plasma sets and found settings that I am quite happy with.

2xM80 VP180 2xQS8 2xM3 HSU STF3 LG 60PS11 Denon 3808 ATI 1506 LCR 2xATI 1502 Oppo BDP-83