Which of these power cords ?

rilbr, same logic applies to the transformer in your devices.
The electricity flowing thru your PC is just part of another power line between the secondary of the transformer in the street and the primary of the transformer in your amplifier. No electrons flowing thru your PC are reaching the secondary which is feeding the actual audio electronics in your devices.
So if you admit that the PC has an influence you cannot reject the fact that everything from the power company also has an influence, it's the same type of galvanic isolation.

@Kingharold It's the same theory as all those high fidelity speakers having the right true sound but they all sound different.