Check this thread:
http://forum.doom9.org/showthread.php?t=124755
Not sure if they come in handy. I've tried Prestige once and while it looked like it could help a tiny bit at first, I think I ruled that out in later experimenting. With RDO and trellis going on in x264, these things have limited effect and question is if they don't actually hurt. Maybe try that CCE-HD matrix at the end of the thread, that might be interesting experiment.