Couldn't agree more.
In the same boat, Audyssey curve set to 450hz for LCR and 1000 hz for surrounds (only because surrounds had a big bump at the 900 mark without correction) and very happy.
I think the reason for this is thus:
When you pick a set of decent speakers, you select them because they come close to your preferred listening curve.
Any upstream changes to the curve (which audyssey or any RCA does) makes it shift and so you end up finding something amiss for music.
By limiting the correction to close to the room schroeder frequency, you get the best of both worlds - accurate bass correction that would otherwise have needed significant physical changes to the room
While keeping the mids/highs exactly as the way your chosen speaker is supposed to deliver.
As for Integrated, have tried AVR, AVR + AB , AVR + class D in all sorts of permutations and combinations over the last 25 years.
TBH, all three sound the same unless i explicitly go looking for subtle differences (which I don't as there is no better way to ruin one's listening experience..lol)
Have left the Integrateds connected just coz I have em already.
For a new buyer, unless they plan to play at 80db or more for extended periods (or have particularly low sensitivity speakers), I always recommend to simply get a decent AVR and be done with it