JCAudio .. no I'm not saying that. What I'm saying is that if you can't immediately explain why your ears hear a difference it's because your theory is not good enough.
Take an example ... digital cables. Basic theory says it's just ones and zeros, and that, so long as the cable is not so poor as to cause the two to be mistaken by the DAC then you'll hear no difference.
But we do hear a difference.
So the more advanced theory looks at the eye pattern of the signal, considers jitter, cable bandwidth (limited by capacitance and inductance), RFI, and impedance matching, and shows that the optimal eye pattern (which really means low jitter in lay terms) is actually quite hard to achieve, and will certainly alter the overall sound.
So I think you misunderstood me. I am not saying that we should measure audio by specs .. of course not, we should measure it by grins :-). That said it is important to strive to understand what are the phenomena at work that put the grins on our faces, so we can make those grins wider and available at lower prices.
I'm an engineer, but I'm a practical engineer. Engineering is about optimal performance at the right price. A wonderful sounding HiFi that costs $100,000 is about as much use as a chocolate teapot to the general population. A slightly less wonderful sounding system, that still sounds very good, but retails for $1000 is going to bring much more pleasure to many more people. However it is also a much more challenging engineering task, only accomplished when one has a very sound technical understanding of what makes a hifi work well.