Warm Tube Amp(s) to Tame Hyper-Accurate Speakers?

jwpstayman nailed my first thought exactly. What SC’s are you using? I bought D7.2’s soon after they came out replacing the former D7’s and in my well treated dedicated listening room with all tubed gear they have never sounded bright per se to my ears but yes, speaker cables make a huge difference in my experience. I have Cardas Clear SC’s and Auditorium 23 SC’s and the Auditoriums really tame the highs with the Spendors.

The Spendor haters kind of tick me off until I calm down and remind myself that there is no reason to give two sh*ts what they think.

System synergy is real. It could be your choice of amp, preamp, interconnects, digital rig, or room or all or some in combination.

Auditorium 23’s are amazing speaker cables. They are not easy to come by new at the moment so you may need to source a used pair. The Auditoriums with my Spendor 7.2’s and with my Devore O/93’s (I rotate them every six months for grins) do tone, texture, timbre, and space better than my Cardas. The Cardas excel at dynamic drive, snap, pin-point imaging, and deep bass.

If you check out the gear used by S'Phile reviewers, last time I checked more than half of them had Auditorium 23 SC's in their arsenal. For ~$900 new they are amazing. 

I hate to burst your bubble but I doubt anything is going to change those Spendors. I have owned many Spendors and they never had an aggressive high end. I would say that the newer D type Spendors are the problem that you describe. I think you will be spinnin’ your wheels changin’ gear. BTW, I always liked any Spendor that I’ve owned!

Spendor D9.2 Floorstanding Speakers

Features:
*Spendor LPZ (Linear Pressure Zone) tweeter*
The goal of every tweeter designer is to achieve linear acoustic output over a wide frequency range. In practice this is extremely difficult. Spendor’s approach to this age‐old challenge is radical, and it works. The Spendor LPZ tweeter is built around a stainless steel front plate which forms a damped acoustic chamber directly in front of a lightweight woven polyamide diaphragm. The front plate incorporates a phase correcting micro foil to equalise sound wave path lengths across the diaphragm surface, simultaneously it generates a symmetrical pressure environment on both faces of the tweeter diaphragm so the tweeter operates in a balanced linear mode. The front plate also provides excellent mechanical protection for the delicate tweeter dome and a smart modern appearance. Imagine focusing an ultra‐high quality camera lens until you see a clear bright image. That’s the effect of Spendor LPZ technology. Our sequential geometry micro‐foil operates like an acoustic lens. The result is perfect focus, uninhibited sound transmission and a very wide listening window. Sound images are vivid, in‐the‐air, as bright or sweet as any music demands.

I second other poster’s comment on cables, without knowing what cables you are using, power, interconnect and speaker, no one can tell you why things are off. Another high probability is speaker placement in the room and toe in, it’s very likely you have placed the speakers in the right spot for the bass to couple to your room, therefore tonal balance is off

Even Spendor D9.2 drivers would benefit from grounding wires. Don't believe me? That's okay, but do try it and I'm sure you'll be bewildered and amazed. Those troublesome sources that sound harsh will suddenly be fine.

If a Conrad Johnson amp can't fix it then you should ditch the speakers. Having said that way back I had a pair of Spendor BC1s and still rate them highly. Maybe things have changed at Spendor.