Can a better power cable make a difference if NOT plugged directly into an outlet?

Your moving system into the dedicated room is huge improvement by it self.As someone posted it will be even more evident making cables changes.Maybe not at first but as things settle and your ears hear the change’s that youve made.

I just changed out all name brand made cable for my diy/parts wires and went with no shielding (alpha 3) on amp and conditioner...just cd player that is plugged into simple shunyata hydra 4 is shielded.Its been a learning experience and to my ears connectors along with conditioner cable seem to make biggest impact.It providing feed for upstream.

@thyname   It's interesting he mentions "galvanically isolated" for DAC's to "clean up  and isolate noise", since doing so introduces a transformer or capacitor in the USB chain, which can change the phase of the signal.  But it hardly matters because this is the analog side of the signal, which is not used directly by the DAC. 

Finally, all but the cheapest USB hubs are already "galvanically isolated" to ensure an accurate clock signal on the downstream USB ports, so I'm not sure where's he's going with the entire message.

@tomrk : If you want to question stuff, please feel free to do so directly with the manufacturer, or get an engineering degree. I have no horse on this race, as I don’t own any PS Audio pieces at this time, nor do I intend to buy one anytime soon. I brought it up simply to illustrate the concept of “noise” in the context of audible buzz, hum, etc.

It’s a bit of stretch to say all USB hubs are already galvanically isolated, but I will not entertain your questioning of this, simply because I don’t have time I can waste. Apologies in advance 

@thyname  "or get an engineering degree"

Already done.

"It’s a bit of stretch to say all USB hubs are already galvanically isolated"

I didn't say all,   But no doubt some manufacturers will put their name on an average USB hub, put a nicer case on it and sell it for a lot of money to convince you it has some advantage over the ones you can buy for $30.

Lak +1 agree 100%