XXHighEnd

Two Audio Engines are available :

Engine#3 = WASAPI
Engine#4 = Kernel Streaming

Both Audio Engines can play in Exclusive Mode only.
Exclusive Mode : The Audio Engine takes control over the whole core audio features of the Operating System, and no mixing or sample rate conversion etc. can be done (implied) by the OS.

While everybody can choose for himself what sounds the best, it is the most clear that Engine#4 is just that. Everybody uses it almost without exception.

Ever back when Engine#4 was introduced this became clear fairly soon, but since then many of the new SQ related (XXHighEnd) features have been applied to Kernel Streaming and not to WASAPI.

It may be nice to know that WASAPI was introduced in the first version of Vista, and world's first to use it for an Audio Engine was XXHighEnd (it took more than a year for a second appeared).

Warning :
It is the most dangerous to reject Engine#3 forever, when this has been done once (by all or by you alone). This is for a good reason :
WASAPI shows a most clinical sound, up to pure technical. Its resolution seems better than enything else. However, the same properties cause it not to be emotional enough. Now :
Many (really many !) environmental things change, which make Engine#4 (Kernel Streaming) sounding completely different, worth 10s Ks of money might you want to spend money on hardware. There is NO reason that Engine#3 won't show differences which suddenly turn out for the better.
But nobody tries anymore ...
It is a bit of a circle as well, because when nobody uses it, nobody encourage to improve om something which really could be better in there. The resolution is such an example.

Let's emphasize in this context that the resolution increased vastly for Kernel Streaming as well (over time and per new parameters) and that this did not debet the "emotion factor" dedicated to Engine#4, so why would Engine#3/WASAPI not be able to benefit from general improvements ?