I have spent hours trying to find any information about this subject and all I can find are theories, opinions and more questions. Since I am really enjoying the cleric, post U50, I would like a definitive answer on the subject. Before anyone replies "turning undead is useless past level 5", I happen to think it is a viable part of the cleric class and can be quite useful especially in reaper mode.

As a cleric you have Seek Eternal Rest which states a sacred bonus to caster level. What about Sacred (says sacred items not the bonus type), hallowed (maximum hit dice of undead turned), and Silver Flame (total hit dice by +6) items? Do all of these bonuses stack? Do none of them stack? Just what is the deal?