I've owned a string of British box speakers over the last 30yrs - a pair of 3-way Heybooks, 3 pairs of Proacs, 3 pairs of Harbeths and now 2 pairs of ATCs.
Tonal 'rightness' and realism has reached a pinnacle for me with the ATCs. The Harbeths were very good, but not really neutral in the bass and a bit 'sleepy' sounding dynamically - where the ATCs have far superior bass IMO and are alive with realistic dynamics.
I think the little SCM19 I own should be much more popular given their quality of reproduction (tonal accuracy and dynamics) - they need a powerful amp, but watts are cheap these days. Does anyone in the world build a more seriously engineered 5-6" mid-bass driver than the one ATC build for the 19's (and scm20's)? - that thing weighs 9kg and makes up half the weight of the speaker!
The active ATC SCM100s I'm listening to as I type this are another level again. Neutral, but marvellously tonally robust and realistic with terrific dynamics. They can play the big stuff with ease but also sound wonderful with delicate acoustic material. Probably the end of the road for me.