OP — I have a few thoughts to take or leave:
I own an NAD M33. I think it sounds pretty good. I’ve been comparing it to my Prima Luna HP Dialogue Premium integrated, using KT150 tubes, in an office sized room. I’d give the edge to the PL, but that’s my ears, my room, my NOLA Contender 2s, etc etc. I will say, I continue to dislike the BlueSound environment. On a less subjective subject, the NAD is not Roon certified, if that matters to you. Unlike earlier released models that are grandfathered in, if the NAD M33 was sold after Sept 2020, Roon will not recognize it pending certification. Many online dealers, perhaps in-person dealers, are pitching it as Roon ready. It’s not. Lastly, reading between the lines of the reviews and the buzz, the focus with the NAD seems to be its all-in-one feature profile. Yes, it’s an accomplishment. I just don’t see a lot of buzz about the sound. Some. Not a lot.
More generally, I think $5k can get you a helluva good amp. And if you are not philosophically offended by Class D, you might consider some of the amazingly well-priced PS Audio amps. They’ve been well-received. I owned the BHKs a few years ago, but I have not heard their Class D stuff. But, on paper, worth a look.
Impedance is emphatically not a crock. Dan D’Agostino would not say that. Nelson Pass would not say that. Bascom King would not say that. Call Nelson and just ask him. Nominal impedance specs (e.g., "this is a 4 ohm speaker," or "this one’s an 8 ohm speaker") may be unhelpful, or perhaps even "a crock." Nomical impedance is sorta just average impedance. But impedance dips are incredibly important, and have little to do with wattage, and little to do with sensitivity. If a speaker has an impedance dip down to, say, 2.0 or 2.2 ohms at, say, 85 Hz, that speaker is going to be asking for a decent amount of current (not wattage) at 85 Hz. And a little amp won’t have what the speaker is asking for. In a way that impacts sound quality, not just volume (which is arguably all that sensitivity numbers tell you; a test tone of 1000 Hz, delivered with one watt, measured from one meter, gives you X volume, in your case 88 dB — although, I suppose if you love listening to 1 kHz tones all day, that could be enormously important).
Turning to the practical: a speaker with sensitivity of 88 dB pretty much never needs 500 watts. Betcha the NAD, at 200, provides plenty of headroom. It was plenty of power and current with my Harbeth 30.2s, with their low sensitivity. And if you don’t feel like really geeking out on impedance dips, etc, I’d vote for you to keep your sights on the 100 wpc and higher amps and chances are you won’t have any power/headroom issues and can instead focus on other priorities (tone, clarity, imaging, dynamics, grip, air, lack of glare).
My two cents. Worth about ... two cents.