Pass Labs AMP’s- What is the best Pass Amp Sound for You from past 10 years

I just bought a Pass Labs X250.8 and am loving it. The rest of the system is an ARC Ref CD8 and ARC Ref 5se, and Sophia 2's. It has the bass weight, extension and slam I wanted (my last amp was a vintage Krell FPB 400cx - so I'm comparing my Pass to the Gold Standard here), and adds a wonderfully smooth, organic mid that is really satisfying. It's got amazing detail, and is very relaxed at the same time - a remarkable combination. Instruments and vocals are fully formed like the real thing, not flat images in space. The highs are all there with a ton of air and detail (cymbal rides and bell hits convey the tone of the cymbal  beautifully [I'm a drummer]) but it's perfectly balanced in the mix, it's not distracting or forward.

With respect to the treble on 0.8 X series amps. Do you guys find there is a good amount of air, detail, shimmer/sparkle in the treble? Or is it a bit rolled compared to other more neutral amps (ie. bryston, boulder)?

250.8 and XP22.

Demo'd a 250.5 for a short while, though not with a pass pre-amp.

Had the XP12 and 250.8 for a good 2.5 years, but then upgraded to the XP22.  XP12 and 250.8 were very good, the XP22 took things to great, and there was a pretty clear difference.  

I had the XP12 and 250.8 combo on a pair of DynAudio Contour 60's, Klipsch Epic CF4's (with a few upgrades), Ohm Walsh 5000's, and Salk SS12's (current speakers that I absolutely love).  I've had other speakers here on demo's.  It's very rare that the XP12 and 250.8 wasn't a nice combo.

Now the XP22 I've heard on the Walsh 5000's, Salk SS12's, Salk Song 3 encore's (friends), martin Logans (Friends), and a couple other demo's.

It's a great combo.  Great Midrange, excellent bass, and all the highs (without crazy brightness).  I did have a nice Levinson here for a while, and it may have had a shade more detail on the top end, but with a little more harshness in the mids.  I felt the Levinson might have been 10% or so tighter in the low end, but with not nearly the oomph.

I talked to a couple people with pass labs amps and they both felt the XA series is 'far superior' to the X series. For those of you who have compared, is this the case? I guess it depends on how demanding the speakers are but apparently the XA series has components and designs that are closer to the XS series and thus is a better performer.

Talking to pass about this they mentioned the X series may have a bit more bass control and more dynamics especially with harder to drive speakers where the XA series might have a more organic midrange and more detail.

I am the original owner of a Threshold 4000, and had it "updated" and recapped a while back by John Soderberg.  Still sounds great when being fed by a Herron Phono/LTA MicroZotl front end.  I would be interested to hear if any of you Pass-aficionados have any experience in comparing the 4000 with recent Pass amps?