Thanks for the feedback. To answer a few questions:

Yes, no problem with bass reinforcement since I have an Epik Empire (dual opposing 15s) https://www.cnet.com/news/the-king-kong-of-affordable-subwoofers/

Yes, I am using as it was designed, as an all-in-one LCR solution.

The imaging and clarity in the store was particularly amazing. That was probably due in part to the fact it was an 8 foot wide demo "room" with an open back, but my setup is still symmetrical albeit about twice as wide.

I rarely listen to this system at reference levels. I would think that the power of the amp would be less critical in light of this, but maybe I'm wrong?

I would probably re-purpose an Emotiva XPA-3 Gen 1 from my theater system which delivers 200 watts per channel. I suppose I could just swap that amp with the Onkyo and see if there's any improvement and then decide to make the jump to the 976 perhaps.