From what I can tell looking at third party testing, DSD128-DSD256 to be best range for the Cyan 2 with respect to noise performance.
I was playing with the DSD1024/AHM7ECB8 combo last night, but there is no way I can run DAC correction for the Cyan 2 while doing this. Just yesterday, I asked Jussi (HQP developer) about what exactly the DAC correction does, where in the signal path does it come, and how important it is, and his response was:
"I'm not going into specific details, also because it is a moving target. It is near end of the DSP process (it is under post-process plugins in matrix). And it is indeed important.
I think the final choice should be yours. Of course from load point of view it depends on how combination of things adds up and whether there is GPU offload available."