HI,
I have CLS IIA's. They are maybe a little harder to drive than the IIZ's. But the speakers are very similar and I assume anything that works well on my IIA's will work on IIZ's. On mine I have had the Mark Levinson No.23 SS power amp (200W/ch into 8ohms) and two different tube stereo ARC amps: the D115 (110W/ch) and currently a D250 MkII Servo (250W/ch). Of these the D250 is far and away the best. Best detail, resolution, imaging, dynamics, micro-dynamics, fluidity, smoothness, soundstage and realness. The D250 is a great amplifier. So are the speakers.
I should mention that my IIA's are subwoofed with biamped dual Kinergetics SW800's. So the main amp does not have to provide deep bass. I have run the IIA's full range with the D250 and it was wonderful but the speakers had limited dynamic range and bass. This is a speaker issue having nothing to do with the amp. The subs solve everything.
