Length of the HDMI cable has nothing to do with lip sync delay. It has to do with the processing in you AVR taking it's own sweet time in getting done and then sent to the speakers while the unmolested video signal goes freely straight to the display.
I think I have to use 150 or 200 on my AVR, I can't remember since I set it quite a while ago.
Klipsch RF-62II, RC-500, RS-400, SVS PC12+,
Def Tech SC8000
Harman Kardon AVR 1600
PS3, Apple TV, Sharp 70" Qattron