Dazzdax, maybe I have an explanation about the crossover of the Sonus being simple, and yet, why of their consuming such a large amounts of current? Last year, I was experimenting with an old Pioneer receiver from the 70s I have picked up from the garbage as well as a small midi JVC system (2002 model) that I had imported from Asia. I was trying to make them run with a pair of EPOS ES11, 87 db efficiency, no crossover, just one cap between the wires and the doomed metal tweeter. This load was supposed to be very benign...and yet, the sound was very distant, muddied, with both...I was running them with a pair of old radioshack wires I had both for non essensial duties...had chopped some and had decided to "solder" them together again.
Later, I ran the same set of wires to my powered sub and guess what, the same muted sound. I swapped cables and there the sub was, reproducing loud, clear volumes and programs.
The point is this, even with copper wire and simple solder, there can be a major hampering in the power and delivery of the signal to some drivers. Eventhough Sonus might have what it seem to the naked eyes as a "few" components, they still might be robbing the drivers of the "original" watts that were intended for them.
Do not get me wrong, people swear by Sonus Faber and other of these rather power hungry speaker manufacturers, but maybe it was the intention of the company to make somehow demanding speakers in order to get clientele who are moneyed, AKA: can afford to have monster amps, rather than some tube loving, hi efficiency owners of SET amps.
To make my speculation into conclusion, you will simply need to have the same pair of speakers, Sonus with one tweeter and one 6-7 inch midwoofer and another of the same type of set up, one tweeter and midwoofer, play the same source or selections for about 2 hours at medium volume. Then, touch the crossovers of the X brand of speaker and the Sonus. If the Sonus crossover components are warmer than the other speakers, then you will be able to determine that the Sonus Fabers soak up the watts and current converting them into heat rather than sound waves. Inefficient, even with a group of smaller crossover components!