Midrange Better Than Harbeth or Spendor?

I second Lindisfarne, you should definitely audition ATC.

Another option might be the classic Quad 989's but you may miss too much of the low end - so I am not sure if everyone would agree that they are better than the speakers you mentioned...although they are obviously better known for a great mid range, as is ATC.

I have a friend with some Harbeth SHL5 and they do sound amazing. And the recommendation to keep them away from walls is a great idea. My friend listens to a lot of classical and I was amazed and how dynamic yet organic the Harbeth's sounded.

As for what other speaker has a nice midrange I would say B&W. I know a lot of people here do not like B&W (maybe they are too popular for "true" audiophiles to like but I had their 804s and 802ds, and while they had issues with boomy bass, and a less then extended tweeter, I really liked their midrange with the FST driver. It may be a little colored but when you just want to relax and enjoy the music, they do a great job and just producing romantic sounding vocals.

I second Reynaud with a good single ended tube amplifier.

Really, the ATCs are so fine. I like Harbeth and Spendor alot, but the midrange of ATCs is less nasal and more open. Downside is the ATCs are VERY critical to source and amplification.

The Ambience ribbons have a fantastically natural sounding midrange-with oodles of resolution and image precision too-and I am a "BBC sound" fan.I used Tangent RS4 and Rogers Export Monitors for years.
In my opinion a good wide range ribbon is more tonally natural than a good electrostat-but most stats are still very good compared to the vast majority of box speakers.
The old B&W DM70 hybrid stats have superb midrange.