Kaiwai:
I can echo the comments of both Duke and Zybar regarding the CS-2's ability to retain their excellent tonality and dynamics at low listening levels. In fact, I find myself listening at lower levels that I used to, because I can!
The outboard crossover requires NO adjustment to set-up. You push a button to recall the distances to the wall behind the speakers (3 feet, 4 feet, etc.), push a button to choose one, and that is it! If you wish, you can read the manual that comes with the speakers and perform all types of adjustments, but I have not felt the need as yet.
I do not know the Leben. The crossover requires balanced interconnects for input (2, 1 each to the L & R channels), as well as balanced output connections (4 ea.) to the amplifier(s).
Best regards,
Dave