Maybe try the Mesa WD-800 the one with actual tubes in the preamp section?
I learned , after trying those few class Ds that I did , ( and after a lengthy discussion with my buddy who builds some incredibly great sounding Class D car stereo systems.) That the tube front end is essential to obtain a luscious harmonic complexity and content with a Class D power section ... otherwise its rather dry. That was most notable for me when I went from the GK MB 800 to the Fusion 800.
I have an SVT
I also have / have had a 7 Pro, Tone Hammer, 800 Fusion, and a Walkabout
Other than an Ampeg tube pre into a power amp, the closest thing to an SVT, by far, is the Walkabout
I would highly recommend you try a Walkabout before making a final decision
I liked the TH that I tried at GC once , but it seemed like a one trick pony ( granted that one trick was great! ) ... but i craved more versatility ( i do some slap solo pieces and breakdowns/interludes)
I found a WA for 500$ ... and I do like mosfet power sections ... but would that amp get loud enough and still sound great pushed?
You said yourself you sold it craving more power ( I have a GK neo 412 cab)
My past experience has led me to these requirements for needed juice:
Tube= 300w
Torodial SS = 500w
Class D= 800w
Cuz of my led handed drummer.
There's a "feel" thing playing through a full SVT that can't be matched
I "feel " this is very subjective and cab dependant .
Plus doesn't really translate through FOH .
I am more interested in the thickness of available girth and the mids.
I just sold my trusty GK 700rb because compared to the SVT ... when I'm in the pocket of a groove , or soloing on the upper register on my bass ... the GK was quite thin , and I feel this problem was related to the frequency response curve of the GK vs the SVT.
The GK is scooped at around 300hz , as the SVT has as mid bump around 400hz.
Which is why most people say these 2 are opposite , or " couldn't be more different"
I also think that relation is what's tied to the "feel" of them .
On that note .... @agedhorse ... do you have a frequency response curve for the Mesa WD800 you could show us!?