I've heard this quality of the midrange, particularly upper midrange, described as "shouty," and that's as good a description of it as anything.
The good news is that far more audio information is reproduced by the midrange of the HS7 than I've heard before in powered speakers. We've all heard cheap powered speakers, also cheap bookshelf speakers (2-way designs). None of that prepared me for what the HS7's do in the midrange. It's mostly a good thing...more information = more clarity and more instrumental timbre/tonality being reproduced (I've heard a comparable effect from high-quality headphones, where the midrange becomes a large, lively, resonant space). Another benefit of this midrange "presence" is that low-volume listening (90% of what I do in home office) is far clearer and more "present" than speakers I've used before on the desktop. I'm not used to be ably to hear music so clearly, even at very low volume (and now in the warm months, with a somewhat muted air conditioner adding its white noise overlay).
The downside is that when I crank the volume, the midrange quickly becomes hard to take...drawing attention to itself. It's not quite as simple as sounding "thin," or "glary" (I've had components that were outright bright from lower midrange all the way--but that's not really the issue here). It's as if a plateau of midrange frequencies is somewhat elevated (3-6 dB? just guessing). It's broad & shallow enough to not sound like a "treble spike" (I've heard that before, and it's not that).
I have a very complicated desktop system, which means I've been able to test the sound of the HS7s with a variety of sources (different DACs; different HP amp/preamps) and wiring configurations. This "shouty" sound is present at loud volumes in all connection schemes & with all components (to varying degrees). I heard it the least when I directly connected the balanced outputs of my Violectric V281 to the inputs of the HS7's. The sound out of the HS7s was slightly more relaxed and refined sounding that way at all volumes, but still could get edgy at loud volumes.
I used the HF setting on the back of each HS7 to drop the level from 2 kHz on up by 2 dB. That helped somewhat--but the plateau of elevated sound in the midrange remains, just being 2 dB lower now in comparison to the lows.
Net/net, the good outweighs the bad. It doesn't hurt that these speakers are very good looking IMO and fit my desktop so well. But still, when I'm in the mood to really crank it, I have to be careful.
PS: a tube preamp may well ameliorate this effect, either by altering tonality, or by distracting from it via heightendd soundstaging in the midrange (or both).
As for your HS7s sounding just right to you, we can never underestimate the magnitude of personal differences. Other might hear my system and be in heaven, even at the higher volumes. Different people show differing sensitivity to tonal anomalies. I'm very averse to elevated treble, for example; and many people welcome it.