So graphically speaking :
Noisy Sine Wave:
Sine Wave with distortion :
So by looking at the graphs I suppose lower SNR makes the sine wave kind of muddy which makes imaging/definition muddy in the soundstage.
Distortion only changes the sound and not the muddiness.
Are my conclusions correct ?
I haven't tried that combo, but I know that the HIFIMEDIY DAC uses the superb 9018K2M Sabre DAC which has a good SNR and killer low distortion, AD900X is also a very good headphone primarily known for its wide and accurate soundstage.
I guess I have to go with the 1600MHZ one as my CPU supports maximum of 1600MHZ http://products.amd.com/en-us/search/APU/AMD-A-Series-Processors/AMD-A4-Series-APU-for-Laptops/A4-6210-with-Radeon%E2%84%A2-R3-Graphics/36 correct ?