Dedicated Pre-amp vs reciever pre-out and Audyssey

[Flatnate]

Okay I am certain this is a noobie question that is asked a lot, so feel free to direct me to any thread where this has been discussed in depth. Here it goes:

What do you gain outside of better Audyssey processing when stepping up in to a dedicated pre-amplifier versus buying a receiver with similar processing, multi-channel inputs and dedicated pre-outputs?

I'll add by saying that I know you possibly get balanced pre-outs depending on the model. Oh..lets also assume I have a great scaler in my blu-ray player and projector and I don't give a hoot about 3d right now, so no worries on the video end of this question also.

For example, running a Onkyo TX-NR708 as a pre-amplifier only versus the pricier Integra DHC 40.2?

Also at what level of Audyssey Multeq is it required that you have a certified Audyssey installer come and run the calibration? I would assume to utilize Audyssey Multeq XT32 to its fullest potential you would have to have this done otherwise the standard Multieq would be the same or similar in performance?

Thanks guys.