there was something in particular about the D7 treble range that made me uncomfortable
I’ve encountered this same criticism a few times, even from a Spendor dealer. I was told the D-line is Spendor’s interpretation of a modern studio monitor.
I haven’t heard the newest Classic 100s, but their predecessors, the SP100s, are still reference-grade speakers IMO. In fact, even among speakers costing upwards of $30K, I’ve yet to encounter any that I think are superior overall. Very few speakers, if any, manage such a wide array of talents. And most are tonally inaccurate in comparison (in my opinion of course).
If you want the sound of SP100s/Classic 100s in a smallish floorstander, get the A7s. My dealer thinks they’re as close as it gets without buying the new Classic range. I did get to hear the new A4s in the same room where I heard the SP100s. Aside from bass output, I think I’d be hard-pressed to discern a difference in a blind listen. That makes the A4s sort of a great bargain IMO.
If you’ve fallen for the Classic Spendor sound, I’m afraid there’s really no substitute outside of the new A-line, at least not that I’ve heard. And no, the Harbeth sound is not very similar.