Seemingly yer Liking the Sugdens.. Often an aquired taste though as some are not amenable to their percieved 'darkness' .
Pertinent info is that these run class A, mostly.
Also that these are fairly pricey gizmos to buy new.
Which limits their market penetration.. some.
Start delving into Class A amps (they make good room heaters as well) for example: Pass Labs and /or First watt and one can go a couple

of steps higher up the sounds ladder.
It's a whole new world $$ allowing, as usual.
Obviously, I have yet to experience the pricier Sugden amplifiers, but if the sound these produce is any indication, I would probably love them. I would also probably hesitate calling the Sugden house sound "dark", especially when pitted against the Regas, which to me sound a bit sluggish, heavy, thick by comparison :sigh:
However, I am pretty sure this particular Sugden pair runs in class A/B, not class A. For one thing, it would run MUCH hotter were it class A; as it is, the Exons runs a LOT warmer at idle, cooling down somewhat while playing. The Sugdens remain cool throughout - though I do mostly play at low levels.
Back to my comparison, I've been doing extensive listening these past few weeks, switching between amps, and I am unsure what to make of it all. If, on the one hand, those that claim all amps sound the same (within their operational specs) are right, I just might be losing my mind; if, on the other hand, I am not delusional and these amps sound very different, I don't quite know which I prefer anymore. Sure, the Sugden sounds more open and lively, making it great for rock, but the Rega sound fuller (sometimes a bit too much so) and more enveloping, like a warm hug, which definitely suits slower acoustic music...
Maybe Sugden's leaner lower midrange blends in better with my room? Perhaps the Rega is activating room modes with an arguably fuller low end? My room really is quite small. I suppose it would be worth attempting to set everything up in a larger room upstairs for a day or two (my significant other permitting) to understand the extent to which my room may be skewing with my perspective and corresponding appreciation of both amps...
Will report back when I have a chance.
As it stands, for the price I paid, I am still completely amazed at what these Sugdens can do...