Ok glad you're getting somewhere - although I wasn't trying to say that 50khz sounds better than 11khz (obviously it does!).
Rather there is a bug in Hatari somewhere (at least in the Windows version - not sure about the others) which causes desync between the audio stream from the emulated Falcon and the audio output from the PC. The desync causes 'chopping' of the sample at regular intervals and it sounds like crunchy audio.
Toggling the khz setting seems to cause it to resync (or get worse). So it's not the khz setting that is the fix, but the toggling effect. i.e. it's possible to get crunchy audio at 50khz too - but toggling can cancel it.
I hope that makes sense.
Still, you may not be getting the same problem as me. It is true that a slow CPU can't emulate the audio accurately - and power saving mode definitely slows down the emulator. I've noticed this while using it.
I have a reasonably fast, 4-core i7 with power saving off, and I still get crunchy audio sometimes until I use the toggling trick.
Best,
D.