At what point can human beings not hear jitter any more? That's the real question. One can split hairs and then split the splits, but at some point it all becomes academic as you say. If 121ps is academic, then what about double that? Then double again? Is it still academic? When does it stop being academic. Where is the line that defines what is "good enough" for 100% of human ears. This is the question that the high end audio industry has a vested interest in NOT answering. The truth is, the last big improvement in listening to reproduced SOUND (as opposed to technology or convenience or storage or editing or recording or mixing) occurred half a century ago with FFRR and stereo. Since then, the improvements have been more and more academic. For listening to home stereos (as opposed to recording and mixing) we long since crossed the line into academic improvements. The people who argue about the number of angels on the heads of pins aren't really interested in listening to music. They just want to whip it out and compare lengths on paper. That's why we see claims of golden ears accompanied by vehement denials of the validity of any sort of testing that generates anything other than more papers covered with numbers. Jitter is a hoodoo. Even in a $50 Korean no name CD player it's well below the threshold of audibility of even the most golden ears. There are things that are hard to achieve in home audio, but a fancy DAC or high end CD player won't get you any closer to it.