Yes of course it is a totally different type of graph.
Making an INL plot of a SD DAC is pointless.

The INL plot in a ladder DAC tells something about the noise you get switching from bitlevel to bitlevel.
This varies from bit to bit.
With DS the 'jump' in output voltage level (quantisation noise) is always quite similar in amplitude where it is not in R2R (be it signed magnitude or 'conventional').
With a few bit DS there are small errors of course but these are much smaller than multibit ladders of course.

Still the sine linearity does say something about how accurate a DAC is but not in the same way as INL and DNL plots.
The SFD is not your typical ladder DAC though and somewhat differently priced from DS DAC chips and current ladder DAC chips.

The question remains how linearity translates to sound quality.
Given the fact that this linearity subject doesn't come up with vinyl/tape, which suffers from even bigger linearity problems (noise and mechanical 'problems' than digital does, tells me linearity may not be that important to obtain 'natural (organic) sound'.

Digital 'processing' of the signal, upsampling algorithms, DAC chip implementation, signal routing, PCB design, power supply, electric isolation and post/reconstruction filtering seem more important aspects to me than linearity of a chip in the DAC-device.
It stands to reason linearity should be good and at least a decent ENOB should be reached.

One thing I've noticed is that companies like MSB - their higher priced DACs have the more linear modules - the MSB DACs sound basically the same tonally as we go up - with the only difference being better extraction of low level information.

Could it be that in the case of these DAC's the perceived difference in SQ is NOT just DAC linearity related but could just as well be caused by more careful/correct implementation of Digital 'processing' of the signal, upsampling algorithms, DAC chip implementation, signal routing, PCB design, power supply, jitter reduction, electric isolation and post/reconstruction filtering circuitry ?

Except for the obvious digital and analog filtering all the other aspects have nothing to do with tonality and can make a difference.

I think you completely missed my point. 

What I said was that good SQ is not solely determined by linearity but the other aspects I mentioned as well.
You just now assured me they nailed them, so all aspects that lead to 'good sound' are there which was my point.
Its not just linearity, its ALL the aspects that need to be O.K.
Should you have any proof that the most expensive version and the cheapest ones ONLY differ in DAC module (linearity) and THAT's what causing them to sound different/better then I will admit publicly that I am retard. 

I may not agree with everything that is written, stated or believed to be 'true' just like you (and a few others most likely) don't agree with what I have to say (and do).
However, you won't see me telling Marv (nor others) they are retards nor that they are indulging in placebo.
Please don't put words in my mouth.
I feel I am free to question everyones thoughts, debate, offer counterpoints and everyone is free to reply (in a civilised manner).

I simply post my opinion, just like the rest of us here, even if you don't agree or don't like me or my opinion.

Looks like Metrum recently announced a new OEM DAC module, chip, something like that (I'm guessing it utilizes the DAC8581 still): http://www.transient-audio.nl/

"The Dac One is a modern high precision replacement for old dacs very often used in "non oversampled" systems like the old TDA 1543 and TDA 1541. It is not a pin compatible replacement but a way to build up an converter system which can meet the best systems today in terms of sound quality.

The Dac One is build up around a fast 16 bits and very accurate R2R ladder network. To match this ladder network to real audio formats,  fast glue logic is added and makes the dac compatible with RJ16, RJ24 and I2S standards. Like one bit dacs, the Dac One can handle 24 bit resolution due to forward control techniques as realized with our FPGA based "Forward Correction Module"

The ladder network is designed as a current output device so to get a voltage out an I/V converter is needed. Depending on designers needs the Dac One is available in both current and voltage output versions."

Specs (actually lists LSB accuracy and differential non-linearity): http://www.transient-audio.nl/Technical_Specs.html
Datasheet (not as much detail as you might hope): http://www.transient-audio.nl/Dac%20One%20datasheet.pdf

I noticed this reports lower THD than the Metrum DACs as well, 0.008% vs 0.03-0.04% (Hex measured between 0.01-0.02% when I had it, but official specs say 0.03-0.04%).

Also some recently posted PDF on Metrum's design philosophy. Not that I necessarily buy into some of this, despite liking the Metrum sound, but some interesting ideas: http://www.metrum-acoustics.com/Design%20Philosophy%20Metrum%20Acoustics.pdf

I think it was solderdude that was curious how NOS would change measurements after going through the chain and coming out of a driver. I noticed the Metrums I tested did NOT sound right if you played high frequency sine waves, especially above 10KHz, unless at levels well below 0dB (to be fair, music likely isn't going to have treble signals at 0dB). Think dial-tone from a 56k modem. The NOS1704 sounded pretty regular up top in comparison, but also had considerably lower measured THD. Both have weird looking sine-wave results straight from the DAC if you test with an oscilloscope, but I have been meaning to run some more tests on HP measurements to see how NOS DACs affect them. Unfortunately, I just sold everything but the Classe DAC-1. Some day...

I had the same thought when I read that. I was going to make a joke earlier that Metr...uh, said DAC manufacturer was saving software trimming for future, moar better products (assuming they don't trim already based on measurements)...and now I'm wondering if that would not have been much of a joke.