Thanks again. I have narrowed my choice to harbeth vs ATC.
Either will make a great choice and should make you happy.
IMHO, Harbeth's excel at lower volumes with a lovely midrange and warm delicious sound. ATC's prefer to be driven harder as they have a very precise tight punchy bass (sealed box low Q). Depending on your music tastes and how well the room is treated one may work better than the other.
ATC's midrange could easily overpower a small untreated reflective room without carpet - too harsh - so vocals and pleasant sound may favor the Harbeth. However if you want detail in large orchestral classical pieces or big band jazz then ATC will probably carry the day. Horses for courses - remember Harbeth's tend to be used in broadcasting and drama and excel in speech intelligibility and natural non-fatiguing sound whilst ATC's are more like a race horse (rock, movies soundtrack and classical monitoring).
Are your listening preferences more towards going for a nice pleasant enjoyable trot in the countryside or do you want the exhilaration of tearing around the race track? Or put another way, if you like drums with a kick drum and crash that sound like the real deal then ATC will float your boat (for others it may drive them from the room...)