A lot of people here and elsewhere will also talk about things like: it is what you hear, and implementation that matters....not which ICs, or measurements... blablabla... As I always maintain, that one cannot argue about what one hears. It is impossible to prove or measure the validity of subjective measurements. Objective measurements are provable and repeatable. Also, engineers who design the best audio gear rely on facts and theory, and to them measurements are indispensable, though of course they also do listening tests. That reminds me of what I read about Peter Walker's once said in an interview (quoted below) many years ago. On your point of the choice of the DAC chip vs implementation, I would consider both important, and it would seem like not a good idea for a manufacturer who claim better implementation, but would opt for a lesser DAC IC. Wouldn't it make more sense to not give their competitor an excuse and marketing advantage by using a comparable or better DAC IC? Or they simply use "implementation" as an excuse when the real reason for not using a better IC is mainly the all important "cost"?
For those interested, Peter Walker, a highly regarded engineer apparently once said the following in an interview with the Audio Amateur in 1978 in the Quad factory:
For those who don't know how good Peter Walker and the Quad 303, 405 were, just ask
@TLS Guy and I am sure he will have good things to say about him and those amps.
Subjective measurements of "sound quality" is subjective and will naturally vary among the individual listeners. Even then, it would likely be not deemed reliable by most experts if not done in a controlled DBT session. And then if you throw in the effects of different DSP functions including Room EQ, it just gets so complicated that it would be impossible to conclude one way or another. Even just to compare using direct mode, not too many hobbyist would have the resource to try several or more different AVPs in order to find out which one they prefer as it would be very time consuming even if money is not an issue. Going by specs and measurements would seem like a reasonable/viable alternative imo. Good engineering and build quality should lead to good sound quality too in terms of accuracy/transparency. Again, at least one design engineer, Mr. Walker seemed to agree.
By the way, I also might have suggested the OP to consider the Anthem AVM70 too but he seems to be considering the MRX-1140, not the AVM70.