Swapping W4S to Pass Labs XA- worth it?


I currently own Wyred4Sound ST500 MkII powering my Golden Ear Triton 1s. 
Before it was Krell 400xi - and def felt W4S sounded much better -cleaner and (surprise) warmer. I am using it in HT setup or in separate "analog" path.
But upgrade bug is strong ))) and I read somewhere that GE uses Pass Labs XA in all demos.
I wonder if it worth to upgrade and will I felt improvements. Speakers are 92 db sensitivity, and low bass is powered.
Have anyone compared W4S mk II and Pass Labs XA 30.5 or 30.8 (I cannot afford more powerful Pass amps)?
mikhaelkuz
Well, I decided to pull a trigger on used 30.5 (late build, less then 2 years old). 30.8 is simply too big for my rack and will stick out too far. Will report results when all received and set up )))

PS I am not using preamp, instead I am switching amp inputs via Rolls SS32 switch, a very well build simple device
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Hello Michealkuz, 
Congratulations on getting this amplifier and I believe that you'll be very happy with your decision.  Given your (stereo) listening volume habits and music genre  I doubt  you'll use more than a few watts (the majority of your listeniing) and will rarely move out of class A operation. Let us know your listening impressions. 
Charles
OK, as I promised - reporting on Pass XA30.5.
Listened to it for more then 2 weeks now
It is definitely better, then W4S. The difference is not "night and day", definitely not like AYON CD-5 vs OPPO-105. That was night and day, with Ayon blowing me really out of the water. This is more like "night and dusk" so to speak.
I am not reviewer and cannot describe all in audiophile terminology, but sound is more "natural" for my ears, and more detailed at the same time. Especially on small classical quartets, music I heard live very often - cello is spot on, which I never was able to achieve in my system for years.
Imaging is actually very close call - may be W4S ST500 II amp is pretty good indeed, as some other people say. It is just not Pass Labs.
With my GoldenEar Triton 1 needle on a meter almost never moves. I have to crank sound to level I feel uncomfortable to see it start to move slightly.
Two additional observations -
1. I can hear more details with lower volume then before, surprise.
2. In HT settings (I recalibrated system due to different amp gains, I use Anthem 720MX as a processor) and for 5.1 recording sound improved quite a bit, more then I expected. the whole presentation became way more organic, and I gave my collection of awesome Steve Wilson classical prog remixes a new spin. Dunno if it is amp or recalibration or both.

At the end I would like to thank everyone who participated in this thread and pushed me into decision to switch amps - money well spent.