Most underrated Audio Manufacturers

Some know you can spend $$$$$$$ for some components and at the end of the day they are sonically not really better than those for 1/10 of the price to others. Well, some sleep well owning those because they have the "test review" under their pillow, some loose the marketing battle but try to push the sonic curtain. What components are among that group in your opinion?
My choice
Preamp: Lamm LL2
Amp: Atma-Sphere
Cables: Signal Cable Silver Resolution
Turntable: Townshend Rock
Phonostage: Manley Chinook
Arm: Rega 300 with Incognito rewire
Speaker: Reference 3A
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Teac. Most of their equipment benefits from its parents technology.
Quicksilver, Fritz speakers
In my opinion several of your choices are not at all underated but get the recognition they rightfully deserve, at least by those in the "know". They would include Lamm, Atma-Sphere, Reference 3A and the Rega 300 of the products I've heard, owned or am familiar with.

I am currently listening to the latest version of the DeCapo speakers and find them uniquely special, independent of any review I read years ago when they created quite a buzz. The Atmas-phere is consistently regarded as SOTA and rightfully so. Does amplification really surpass their level of excellence for all genres of music? I don't believe it does. That Rega arm has been around forever and is just a classic.

I would only add the Berning zh270. I own the amp (12 years and running) but what is more telling is that I appreciate it more the longer I own it. A tremendous value during it's run and when matched with the right speakers I would consider it a timeless performer along with being a simply brilliant design. Maybe superceded by David's latest offerings, at much higher prices. One thing is certain, guys like Ralph Karsten and David Berning don't market "improvements" they deliver on them.
I would add Herron. As I also own lamm. I found the Herron pre and phono amps on par with most of the current top picks at a faction of their cost. My friend owned top anniversary CJ and Audio Research models but at the end, out of his believe, he settled with the Herron.
Spread Spectrum Technologies Ampzilla 2000.

I have found that both the Ampzilla 2000 and Son Of Ampzilla 2000 power amps shoot way above their prices.
Used Dunlavy Speakers still provide the ultimate bang-for-the-buck scenarios for those who have the room for proper placement. An example is the SC-V which can be had used for around 5K and competes favorably with new speakers costing 10x the amount. Over the years I have collected virtually all of the Dunlavy products to include the reference passive subwoofer utilizing 4 10" drivers in individually sealed compartments, along with the SC-Is, SC-IIIs, SC-IVs SC-V and Cantatas. I have formed them up into 2 channel and Home Theater systems with astounding success. All Dunlays are voiced to be identical. All are time aligned to focus in a precise radius.
I go to the biggest Audio Shows every year and walk away shaking my head. To get performance beyond the Dunlavys cost obscene amounts of $$$. Few people who have these speakers properly set-up are ever willing to part with them.
Dynaco, HomeGrown Audio, Jolida, Legend / Von Gaylord, Odyssey, Quicksilver, Shuguang, Sony, Technics
Audio Horizons,Space Tech Labs.
Of the speakers made today to beat the Dunlavy I would pick the ESP Concert Grands and the Roockport Altairs.
Marten Coltrane Alto speakers. I regard these little known speakers as in
the top 4 of the best stand mount speakers ever made. They were full
range speakers which incl: a 9" down-firing Accuton, 5" Accuton
midrange & 1" Accuton tweeter in an elyptical shaped carbon
sandwich construction monococ cabinet, with a heavy polished stainless
steel integrated stand & plinth with adjustable Black Diamond cabon racing
cones. The Alto's sounded amazingly pure and fast, with solid bass when
paired with a big ss amp like Boulder. They could be bi-wired or bi-amped.
The speakers could be placed close to rear walls thanks to their design &
did the disappearing act very well. They also threw a quite holographic
soundstage. The tuning was just right actually. The Altos are way
underrated speakers & a steal if you can find a pair in good shape in their
original boxes.
Quicksilver is great gear for the frills, solid build quality, rock solid reliable, AND they sound great.

I have a pair of Mid Mono amps and they are the best value for the money of any of my components. They are built like a tank and sound so good with Gold Lion KT66 power tubes.
Most Ortofon phono cartridges, and especially in the lower price point models, for the fact that they have historically had excellent positional tolerances from the stylus (when loaded VTF) to the cartridge mounting surface. Allowing for good azimuth and SRA results even with rudimentary set-up methods (horizontal tonearm and accurate VTF) applied. And musically they have offered a wide selection over the years at very good prices with exceptional performance. 
Very good point r f  !
Thoress preamp and phono stage and TW Acustic phono stage.

Among SS amplifier builders, I would say Coda is pretty underrated. They've gotten some reviews over the years, but not nearly as many as some other, much more high-profile manufacturers. They seem to do their own thing (including OEM work) and if reviews come their way, that's cool--and if not, that's fine too.

I've heard or owned a decent number of Coda amps over the years, and they keep getting better. They're not the fanciest or most strikingly impressive, but they make music in a whole-cloth, highly transparent, and effortlessly dynamic sort of way that I find compelling. In short, they just sound RIGHT to me. They've been in the game for quite a while now and clearly know what they're doing. Anyway, just one man's opinion.
I really like croft's little integrated amp and they have a good phono stage. Understated but outstanding sound for the price. 
Line Magnetic Audio
Schiit Audio
Nad's integrated amps, the BEE series, are underrated for sure.  The bang for buck factor is off the charts and you save a fair amount because they aren't shiny bling with thick aluminum face plates.  Beauty is only skin deep, after all.
Gamut audio second to none.
Based on my personal experience, definitely Blue Circle Audio.  Wish I would have tried Gilbert's offerings years ago.  Regards.......

Symphonic Line - under the radar in the US, but absolute top level solid state amplification
Arnie Nudell-era Genesis speakers (at their used prices)
Forgot one; Belles ( Power Modules )!  Dave Belles still going strong as he just released the Aria series.  Regards........

syntax’s original list is still relevant. I owned three on his list at the time of it’s posting. Lots of other excellent nominees have been added since then, but not Music Reference, Eminent Technology, BEL, Van Alstine, Clear Day, and Kimber.