Anybody using Wilsons or Soundlabs with Pass Labs?

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.

The purpose of my post was not to "insult" the Pass Labs X600. I was mearly pointing out that the amplifier's bass performance (Sound Labs can hit 50 ohms or higher here!) is not acceptable. This includes playing the same recording on other speakers and taking into account the expected bass on a variety of other speaker / amp combinations. I also use test CDs that put out bass tones; the Pass just didn't like the Sound Lab impedance. That does not mean the Pass is a bad amp; in fact, when paired with the appropriate speaker, it is an outstanding amplifier.

The true test of being a real Audiophile is acknowledging that not every component in Stereophiles "Recommended List" will work correctly with other products on the list. The key is to build a system where each of the components compliment each other, instead of exposing weaknesses such as impedance issues - low or high. This is not an easy process, but very rewarding when done right.