Can you compute SINAD for a chain of equipment? Some say yes, some say no. I say yes. Consider. You can feed a signal into a DAC, measure the output, and compute SINAD. Based on measuring "the average power of the signal, noise and distortion". And you can do the same for an amplifier. With me so far? Then, you feed the signal into the DAC, connect the output of the DAC into the amp, and measure the amp output as before. You now have SINAD for the DAC-amp as paired. I'm prepared to go a step further, and say that if you have the SINAD of the DAC, and you have the SINAD of the amp, you don't even have to get out your oscilloscope, you just do the math, as described above, and we even have a little snipped of python code for this.
Is there SINAD for speakers? Again some say yes, some say no. Looking at the definition of SINAD
https://en.wikipedia.org/wiki/SINAD my take is that you can still apply the formula even if speakers don't create noise. Just plug in a zero for the noise terms. Maybe that's a misuse of SINAD, let alone the next step of a 3-component long chain of DAC-amp-speaker calculated SINAD. So yeah maybe as was suggested you go back to examining the noise and the distortion separately. (And chain these?) In any event, I'm thinking the key take away, from the math, is that we're in a weakest link in the chain situation, even just looking at the DAC and the amp. But further, the weakest link is the speakers. Given that speakers have a nominal SINAD of 60. This completely dominates improvements in DAC or amp, unless one of those was way down in the SINAD chart.
Reading this
https://www.audiosciencereview.com/...er-preference-ratings-for-loudspeakers.11091/ and still trying to understand any definition of "speaker (preference) score". Found this too.
https://www.sausalitoaudio.com/wp-content/uploads/2018/07/Interpreting-Spinorama-Charts.pdf Maybe I'll not be getting any "speaker SINAD", but will accept that its the weakest link, and just generally want to improve it based on "score".
We could get out into somehow trying to measure "enjoyment", but I'm prepared to believe that a subwoofer would be fun. As much as I like headphones or IEMs, you listen with your whole body.
And, ok the other weakest link is the room. I suggest there’s a lot of bang for the buck in Dirac room correction.