What kind of rear speaker?

I'm putting together a HT for my father, and am new to the whole dipole/bipole vs. direct radiator debate. I've spoken with company tech supports, dealers, etc. Everyone appears to say that the debate has been settled conclusively, but they don't all say that the same option was the conclusion! Some claim that rears are really for ambient sound, and so you should go with dipoles on the side or bipoles in back. Others say that was in the pro-logic days and that dolby digital and dts, with their discrete rear channels, require a direct radiator. With different arguments out there, I imagine I'll get different arguments in here. All opinions would be welcome, though. I've searched the forum archives to no avail. I might even consider changing my own system. I'm looking at either a Kef or Paradigm system for my dad (around $3k for speakers and receiver), and have 3 to 5 hundred for rears. Paradigm mini-monitors vs. ADPs? In my own system, I use Snell C/V front and Snell XA55 center. I'm currently using some Energy C6 floorstanders for rears. Would a dipole work better, or even a bookshelf monopole? Thanks in advance.