Amplifier brand/designer with the most unique and consistent “house sound?”

The house sound is usually purposely implemented to avoid fatigue or harshness of the overall sound.. They look for a “pleasing” sonic signature for “most”.  Thats how PASS designs their equipment. It is a group effort and they ALL listen to and adjust accordingly.. 
Glad we have choices and various types of designers who give us the flavors we prefer.  I chose the Pass house sound overall mixed with a first watt amp which has its own secret sauce blended sound. the combination works for me. Just right of neutral leaning to warm.. 
also should be dependent on the type of music you mostly listen to.
No right or wrong when it comes to preferences.

Here we go with semantics again.. 
Pass tunes their amp to sound its best based on a group of people listening and adjusting the final sound to their liking. They always seem to measure well and with low distortion according to the reviews. dartzeels lastest amps don’t really measure well either but that doesn’t stop them from being considered amongst if not the best out there.
First watt is a different animal.. minimalistic amps , low power with no feedback, little feedback, added distortions, etc  They aren’t mainstream and need to be properly matched. Sometimes they feel the need to add feedback to get a better sound, Sometimes they don’t use feedback at all. Whichever FW amp you choose, it’s clearly described on how it’s designed and what to expect.. I didn’t choose my amp based on specs or types of supposed distortions.. but what it sounds like in my system..  

@optimize
“It would be interesting to compare ACA against a ncore. NC400 that is on the other end of the scale and is one of the best measuring amps.

I guess that NC400 is one of those amplifier without any house sound with almost no distortion at all.”

I built the Pass ACA amp, the 1.8 with 8wpc, and use it in my office system. I also read the review on ASR about it before I bought and built one.. I’m driving a pair of NHT S1’s with them rated @86db sensitive.. This is when ASR lost all credibility with me as the ACA amp just sounds GLORIOUS and produces all the volume I need and then some !! I also owned a pair of Bel Canto Ref600 monos based on Bruno’s Hypex NC400 modules for a couple of years. I’ll take the old inefficient Class A topology w distortion and low power sound over class D specs and sound anytime ! I liked your system vid... sounds good even with crappy phone..
Here is one of mine.. my first iPhone crappy recording..
https://youtu.be/vqMqGV342m0
https://youtu.be/yB12zq-UKHI