To Harbeth or not to Harbeth, That is the question...

Low listening ,vocals, acoustic music. The P3ESR is the Harbeth you should be looking at! 
https://www.youtube.com/watch?v=mqFIaiPT_kY

I've owned the SHL5, Monitor 30 and P3s. IMO, the SHL5s had a bigger, smoother sound and are more tolerant to equipment and cables than the others.  That said, I would definitely use a good cable, stands and amplifier with some guts.  I happen to love my P3s right now.  Very well balanced with satisfying bass and good at lower levels.  Using with a Heed Elexir 50 wpc integrated.  

I've owned the P3esrs in the past, and currently own M30.1 (home office) and SHL5+ (media room). As much as I love Harbeth, I don't think they are particularly satisfying when it comes to low level listening. They're not bad per se, but if that's your goal I think Klipsch Heritage series might be a better option. Personally, I don't care for the Klipsch sound (or most high efficiency speakers for that matter), but they really do shine at low listening levels better than other speakers I've heard.

@voodoochillin - I rotate between a Hegel H190, Forte 1A and a pair of Ampzilla 2000 2nd Edition monoblocks (Bryston BP26 preamp).

My SHL5+40s sounded great with the above SS amps. Best with the Ampzillas at higher volumes and with complex music (concertos, symphonies, big band jazz).

A few months ago my uncle gave me a Jolida SJ502 tube integrated. This is my first tube amp and I have only used it at my new place.

They really shine with the Jolida. Different in many good ways. Perhaps lacking a little bass compared with my SS gear. Can only imagine how they would sound with a higher end tube amp.

But this is where the subwoofers do their thing. And very nicely.

I also have used them in 4 different rooms. A 10’ x 12’ office and then an open space 14’ x 16’ living room at my old place.

My home office at the new place is 13’ x 16’.
There is also a 15’ x 19’ living room.

I have run them full range with and without subwoofers (4) in all mentioned rooms at both places.

I can definitely vouch for the high quality low level listening.

Hope this is helpful.

Agree 100% with @chayro 
 '' I've owned the SHL5, Monitor 30 and P3s. IMO, the SHL5s had a bigger, smoother sound and are more tolerant to equipment and cables than the others. ''

Very tolerant with the numerous amps, cables and stands that I have used.