There will always be a debate of measurable hearing and the psycho-acoustic phenomenon. I think it would be a little arrogant to assume that all acoustic energy ceases to be just because we cant measure it with a tone inside a controlled environment.
The very nature of a pure analog chain distorts harmonically, so whose to say what excitation factors are truly occurring in the harmonic spectrum above these established ranges.
But todays digital format works within measurable designed parameters, where analog is not in the respect that its some sort of a happy accident.
With that, whose to say with all of the budget converters and speakers on the market what accuracy within the digital realm is still intact from beginning to end. Theoretically it maybe identical internally, but it still has to be converted to hear it.
So with the obvious debate on sampling rates, there is less of a debate over bit resolution as detection of the accuracy of amplitude characteristics and attack transients, as subtle as they may seem to some, are slightly more noticeable to SOME than the supersonic frequencies. So for the sake of your post, in the most general of terms, and assuming you are all digital, I'd be more concerned over your bit resolution that your sampling rates, especially if processing power is an issue.