so basically, I can use a cheap AVR and it wouldn't be different from an expensive amp? That seems to be what everyone is arguing. I just don't believe that with the logic presented..
That is not what I said. You claim to be very happy with your speakers. So it would appear your receiver is driving them satisfactorily. Some speakers present troublesome loads, and do require better more powerful amps. Usually it comes down to not just better sound as the receiver amps become overloaded, but an issue of reliability, as speakers vary in their ability to blow up receivers.
I personally do not use receivers, for lost of reasons. I use pre pros, and I have good test gear. They measure as good as most preamps, I have tested, except in one important aspect and that is head room. So that means you have to be very careful about gain structure, in the system design. There is no deleterious processing going on unless you engage those equalization programs like Audyssey or YPAO. So leave them off. I would suspect the preamps of the higher end receivers have comparable performance.
A properly set up AV system running in two channel should be every bit the equal of a stand alone two channel system. So you do not need to have separate systems for AV and music. That is utter nonsense.
The fact is, the sound of your system is dominated by your speakers and their interaction with the room. However speakers are the most dominant, but careful placement decor and furnishings usually suffice to optimize the room. I have never had to resort to special acoustic treatments,.
It is easy to show that speakers are dominant. If you go to a good dealer who can switch from speaker set to speaker set, you will find that the sound changes significantly. That is not just confined, to speakers between brands, but between speakers in the same brand. So I usually naughtily ask the salesman: - "which one is correct?"
Unfortunately these days it is design by committee. My point here is that it takes years of experience as a designer, to produce a very consistent sound and sound stage between designs. I design all my speakers, but the very last skill I acquired was the ability to have a consistent sonic presentation. I can honestly say that only comes with experience, as there is still a large area of judgement involved with speakers.