Do you actually sufficiently play with all the different settings in XXHighEnd ? Like KS Adaptive Mode vs. Special Mode ... Latency ?
I use version 09-y7. The newer versions don't work. I can not choose KS-modes or the engine, for both of my soundcards (USB/SPDIF and RME Hammerfall HDSP9632). If I play a file, the player starts but after some seconds it tells that there is no file.
In version 09-y7 I can just use enginge 3 but this is not your fault. It comes with that driver I think which has a windows avoiding kind of KS included.
I played with the q1 slider. After setting it to "0" I feel it could be very good. It is with less "grain" ("grain" probably exaggerates but I know no better word..) Comparing to the PD-S707 with a Bach CD I would now prefer XXHE. But that is just for today. These impressions change so easily.
My latency was about 120-130us before I reinstalled the OS. Now it is about 140us. I have not shut down any services so far.