Are Harbeth the only warm and euphonic speakers in town ?

How about some Vienna Acoustics Hyden’s?  There have been a number of versions over the years, but they’re all quite polite. 

Kef ls50. The original today are an amazing affordable masterpiece. 

ADS L Series.  Beautiful mids.

Why is it that so many people are gunning for Harbeths?

I'll admit they won't suit everybody, but they are the only speakers I have ever owned that don't have me itching for an upgrade.

I’m surprised no one has mentioned Magnepans. I have the Harbeth SHL5+ speakers and love them. I wouldn’t describe them as warm, however. They sound very detailed and natural in the mids, and without coloration. After owning Klipschorns, Tektons, and others, these are my endgame speaker. Based on what you said you’re looking for, I think the Harbeth 30s would suit you perfectly.

I also have Magnepan 1.7i’s and LRS speakers. The Maggies have very nice, rich mids. For me, the Harbeths are superior to the Maggies in most areas, but the Maggies sound very nice, and I enjoy switching them into the system every now and then. I would suggest that you’re on the right track by making tonal quality a priority. There are plenty of speakers with a detailed, analytical sound, but I greatly prefer the organic, natural sound of the Harbeths and the Maggies.