Then I look at receivers and I'm disheartened. I don't want to spend $1,200 on speakers if they're left lethargic by an underperforming receiver. Don't get me wrong, I know performance is expensive. I'm willing to settle for 90% of what these speakers are capable of, but these receivers barely break 50%. I'm not going to drop $1,200 if I can't get my money's worth.
I guess I don't understand what's leading you to these metrics. I don't think any of the AVRs we're discussing are going to 'barely break 50%' of the performance of Kef Q550s.
Most of the AVRs in the chart have SINAD above 70. That's not great, but it's not going to be audible in casual HT content and music listening to most people. Are there edge cases in focused listening on familiar content when somebody would be able to tell the difference between 74db SINAD and 100db in a blind test? Yeah, maybe, but it's going to be a subtle thing, definitely not 50% vs 90%. Many of the people on this forum use miniDSP units for roomEQ which likely also have terrible SINAD relative to other electronics.
At the budgets you're talking about personally I would not worry too much about the AVR flaws discussed in the reviews of this website. They're very technical issues and they are most likely swamped by things like not having enough power or not having any RoomEQ.
1) Make sure you have enough power(use a basic calculator, or learn how to do the math more accurately yourself courtesy of Dr. Toole).
2) Get a Denon or Marantz with "Audyssey MultEQ XT32" specifically(not MultEQ alone).
Don't try to chase 2-channel DAC SINADs with your budget. It's not practical. Getting it in a multi-channel setup is currently expensive and/or challenging, and that's something Amir's reviews are trying to change, but there's no easy or cheap workarounds right now.