Charles1dad, I'm not an engineer, but try to be a pragmatist. I also stayed at a Holiday Inn last night. LOL :>')
I think others have made the point that amp and speaker designers have to make trade-offs to achieve a certain result at a certain price point. I appreciate that there are a number of "tube friendly" speakers on the market (I am aware of at least 3 or 4 off the top of my head), but I suspect that most are not. Consequently, I surmise that most speaker designers assume that their gear will be driven by high output SS gear and if compromises have to be made, it could be impedance and phase angle attributes.
So maybe the real issue is that while tube amps possess certain sonic attributes that SS amps can only hope to mimic, perhaps if something has to "give," tube amp manufacturers will have to figure out a way to make their products able to do double duty and handle speakers that are designed and voiced to be driven by SS amps. Ralph and Al have made a point that such amps are heavy and costly. Perhaps that will be the design challenge of tube amp manufacturers if they want to compete in the present and future marketplace.
In the meantime, I have tweaked and configured my gear whereby I am better able to enjoy the music without experiencing listener fatigue. I don't know how flat the FRs of my S8s are, but the output is musical. I'm standing down for now with respect to switching out gear. Next time, I'll be a little smarter when putting gear together. We all live and learn.