... abit confused: how does a power cord affect the presentation of sound...

I'm new to the whole power cord thing too.
I've been learning quite a lot in this forum about how the power cable affects performance of the devices they power.

One of the first ideas that I hadn't even considered is the fact that the power cable is pretty much somewhere  in the middle of the circuit past the circuit breaker.

Alternating current goes through a conductor of the Romex in the walls, to the outlet receptacle, through the power cable plug, through the power cable, through another plug, into another plug in the device requiring current, and to close the loop for the potential, through the other pin in the plug on the device being powered, into the plug on the power cord, through the cord, to the plug into the outlet receptacle through the other conductor of the Romex in your power box.

The AC power has 4 connector points through which it must travel from the circuit breaker to get to and from the device requiring current, not taking into account the ground. The materials and quality of those connections is also a contributing factor.

This is why I must logically agree that running dedicated power runs (also isolating it from other devices in the home), and higher grade plugs will allow for better electrical connection, plugs at the wall and plugs in the cable where any deficiencies can be overcome.

I wanted to discover for myself if any benefit could be observed by changing my factory issued power cord out for something different? I can't remember names, but a few suggested Synergistic Research Master Coupler as a good start for a test.

The Master Coupler X2 did improve the system sound when I plugged it into my power amplifier. I was converted to power cable upgrades, because my ears told me there is something to it.  

To answer the OP's question, I found that PCs can and will affect the dynamics and the size of the soundstage. Doing that, all manner of lessor effects happen.

Don't fall for the red herring of "all that romex and junk" the power goes through before you get it. All that came before it is moot since what you need to do is get the best you can from where it all terminates: the outlet.

When you cook a steak, do you worry about the rest of the cow that came before it?

All the best,
Nonoise

This is just beyond me. Nothing matters but the power cord from the receptacle to the component? The panel box,  wire in the wall, transformer in the component that isolates the primary from the secondary, filtering in the component none of this makes a tinker's damn only this freaking 4 foot power cord?? Jesus Christ people  learn how electricity works. 

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/ecircon.html#c1

I can easily hear the differences when changing IC's or speaker cables in my system but struggle to hear any change at all when inserting a new power cord....and I don't know why nor do I really care.