Antoine - An interesting move adding the tX-USBultra. I can only speak for my own experience, but I do prefer the tX in my system, and this holds true in all cases with it between Mutec MC3+USB and the microRendu, the old sMS-200Utra or the Neo version. I know what you mean by "relaxed", but I would go with cleaner and more dynamic, which is a slightly different emphasis perhaps.
One thought that I have. Have you considered trying the system without the MC3+USB and running direct to USB? It seems that with the Pro all inputs are now pretty much equivalent, all other things considered. Add to this, myself and a couple of other forum members found a nice uplift in SQ using the MC3+USB with the old Expert, but not so much, if at all, with the Pro. Speculating here, it is almost as if the internal clocking in the Pro is now roughly the same as that in the MC3+USB, hence neutralising its benefit. So considering you are now running the all-conquering AL NUC, it might be well worth trying NUC, tX-USBultra, direct to USB? I am mindful here that your case is a little different, as you have your MC3+USB powered by the SR7, but it might be worth a try one day, if you are so inclined.
One thought that I have. Have you considered trying the system without the MC3+USB and running direct to USB? It seems that with the Pro all inputs are now pretty much equivalent, all other things considered. Add to this, myself and a couple of other forum members found a nice uplift in SQ using the MC3+USB with the old Expert, but not so much, if at all, with the Pro. Speculating here, it is almost as if the internal clocking in the Pro is now roughly the same as that in the MC3+USB, hence neutralising its benefit. So considering you are now running the all-conquering AL NUC, it might be well worth trying NUC, tX-USBultra, direct to USB? I am mindful here that your case is a little different, as you have your MC3+USB powered by the SR7, but it might be worth a try one day, if you are so inclined.
1000 Pro - KEF Blade - iFi Zen Stream - Mutec REF10 - MC3+USB - Pro-Ject Signature 12