Yes - I did. I tried a Pass Lab X600 with a pair of Sound Lab Auras (similar to Milenium series, but made of steel like Ultimate).
I also got to compare the X600 with Krell KSA 300S and Atma-Sphere MA1 mkII.2 OTL tube amps.
The results:
Atma-Sphere had the overall best performance, with the Krell a distant second. The Pass amp had NO BASS whatsoever to speak of. I suspect the Pass amps do not like the high impedances that occur in the mid-bass region.
DO NOT recommend you pair the Pass amps with Sound Lab speakers. However, I will say that the midrange and upper frequency performance was outstanding.