Thinking of replacing my Bat spaceheater with class D, real world thoughts please

Its not surprising that W4S are  good listening.   They were Cullen in their previous iteration and were making the class D amps for PSA back then.. The internals I suspect and I don't know more that that-- If I recall correctly.        Class D   can excel depending on system synergy... just like any other setup.    And a credit to its capability and sonic  virtue--Im using a diminutive  $180 Trends class D without readily discernible dysfunction.  Certainly would have to A/B with another amp to perceive the difference  and  those I have here all cost much more as well.    

I've heard the  Jeff Rowland class D integrated driving speakers similar to mine (one up in the model chain) and was very impressed.. that coming from a SET guy.

My Martin Logan Ethos speakers come with a 200 watt class D amp to drive the active woofer. It is pretty easy to get a 30-day trial period with many products...so recommend the "try and buy" for your own system. An audiophile friend of mine and myself heard a $300k system and neither of us thought it was as good as our much less costly setups...all in the ears of the beholden.

I actually went through something similar to you, although in a different step. Like class A, A/B or tube not all are created equal. I think once you get to top quality gear it comes down to a matter of preference. 
I was bryston fan for years and was interested in tubes but didn't like the lack of power. I started auditioning different class D amps and liked the bel canto's a lot , I thought the nuforce's were decent and the Rowlands were nice but not a huge difference from the brystons. I came across spectron (musician ii) and it was a relevation. I then added another to run mono and had them both upgraded to hybrid plus status. I think spectron does class D correctly and enjoyed them for years. IMO they have the muscle of the brystons and the smoothness and detail of tubes (more of a KT120, not warm like KT88). 
I enjoyed them for years but something was always missing for me , and after a while I realized it was the midrange. I could listen to Floyd all day and be mesmerized but it never got Lou reed right to me. 
I actually was audioning BAT because I wanted something warmer but I changed my speakers shortly after and heard some of the belles stuff and never looked back. You always gain/lose something when changing equipment for the most part but that Belles SA-100 just didn't everything right for me, I since upgraded my tube pre to a belles LA-01 and the combo with my Vandersteens is breath taking. 
You can not tell my set up is all solid state, it has power and smoothness like I've never had in my set up. I did lose some low end but what I gained everywhere else is amazing.
It all comes down to system symmetry but I can tell you for class D the Spectrons are something special. 

I have the NAD M12/M22 combo which as far as Class D is concerned is fairly high end.  They measure great and don't have any any of the etched/digital sound to them.  They are pretty smooth and about a week ago I would've sung their praise.

That is until a week ago when I took them to a very high end dealer to audition some Sopra 2's. Their room is pretty heavily damped and it acts like a microscope for any changes in gear or cables.  I'd never experienced anything quite like it, you can be VERY discerning in this room.

To cut to the chase, my NAD setup felt DRY and lifeless in there compared to the Class A/AB amps we listened to.  I didn't want to admit it at first because it's deflating to hear your gear getting outclassed, but they just were.  We swapped cables out, amps, preamps, different speakers, etc. and the main culprit was the NAD M22.  

The dealer even said this was THE BEST Class D he had personally heard though he didn't carry any Class D as they carry a stigma whether warranted or not.  And to me they were just simply getting outclassed by some decent but not over the top Class AB from Pass, AVM, and Simaudio.

Way more musical with much better tone, more harmonic richness and bloom.  Deeper and wider soundstages, you name it.

YMMV