This is really a tough one. I've heard both, unfortunately at 2 different locations with different electronics, so tough to accurately compare. Honestly don't feel you can go wrong with either. As usual the real answer is to let your ears be your guide - the problem is that Harbeth speakers are almost impossible to find (I heard them in a private home).
I've owned Spendor speakers for over 25 years, currently have the tiny S3/5s in my study and simply love the Spendor "voice". Classical, jazz (and vocals) are my preferences too.
You might want to read the review of the Harbeth Monitor 40s at enjoythemusic.com by Bob Hill. Bob was long a Spendor advocate but recently switched to the 40s. While the speakers aren't 7ES's, his reasons for switching might be helpful.
Good luck on you quest.
I've owned Spendor speakers for over 25 years, currently have the tiny S3/5s in my study and simply love the Spendor "voice". Classical, jazz (and vocals) are my preferences too.
You might want to read the review of the Harbeth Monitor 40s at enjoythemusic.com by Bob Hill. Bob was long a Spendor advocate but recently switched to the 40s. While the speakers aren't 7ES's, his reasons for switching might be helpful.
Good luck on you quest.