I have not heard the Harlekin and am unsure what they look like and have for drivers. That said I have heard the Acapella Violincelos with the plasma tweeter.I heard them in a very revealing system in a well prepared room.
The sound was nothing short of stunning! The ease of upper frequency is so superior to ANY tweeter/panel/driver I have heard. I love English choral music and those little boys can really task a system. The Acapellas portrayed these explosive sounds so easily and realistically;the music brought tears to my eyes. These beauties sound big and image very well. Mike also has subs and this combination made the house shake when the Kings College organ played their big 32ft. reed, yet they are well balanced with the horns. incredible!
Sadly, they are out of reach for me,other than to show up at Mikes (with beverage).
I feel privileged to listen to them as often as I can.
The system was made up of a Einstein line source,Atmosphere m60s (later replaced by Einstein OTLs),Bergman TT/Einstein MC.Morrow reference 6 cables throughout.
I heard this incredible system at Mike Morrows. (This is my shameless plug for a friend)
If you are in the states and looking at these you can schedule a time with him for a audition. He has his own website which is well done and easy to find.