I have no views on the PS Audio Jr other than that it is pretty pricey. I have not seen any proper tests with measurements done with serious lab gear like from Audio Precision. The currently best one on that is probably the Benchmark DAC3.
By and large I don't believe there are many meaningful sonic differences between well designed electronics, whatever the subjectivists on this forum want to believe. If there are differences, they are not necessarily for the better (e.g tube sound). The straight wire with gain criterion was met ages ago with solid state amplification, and I am increasingly inclined to believe that the same is now true for DACs. I am using the analogue output of the Chromecast Audio, and cannot hear any issues, even on a revealing system with Quad electrostats. Even if there may be a slight sonic degradation playing 16/44, it must be small, and I am also pretty sure that relatively affordable DACs like the Sonica, the Pioneer U-05 or the Teac UD-501 are as good as it can get. If you look at the measurement data for such DACs, you can see that frequency response, distortion and noise levels are mostly quite a bit better than for amplifiers, so they are not an problem. Electronic perfection has become pretty cheap, and there is nothing more perfect than perfect, given human hearing limitations. Those who believe they can hear differences between electronics are never able to repeat their insights under controlled conditions.
With electronics the three things that really matter are:
1 matching gain structure to avoid clipping. An example is the 2.0 Volt rca output of many digital sources and the too sensitive line inputs of many amplifiers.
2 insufficient power to prevent output clipping in dynamic music. In a largish room a few hundred watts per channel will do no harm.
3 load independent flat frequency response. Real speakers have varying impedances along the frequency spectrum, and some amplifiers' frequency response is far from flat under such realistic conditions (see the graphs in Stereophile - the audible limit of non-flatness is about 0.2 dB). Many tube amplifiers are very bad at this, hence their individual sonic signature, which is nothing other than an engineering shortcoming.
This is not to say that audio systems cannot be improved, but the weak links are the speakers, with their far bigger deviations from the flat frequency response, and much higher distortion that we would accept from any piece of electroncis. Finally, there is the issue of room interaction. Look at any in room response graphs and you will be horrified.