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

Hahaha. 
All jokes aside, going from one sub-$200 cable to another will get you very little ROI if any at all. I’d go for a used Audience AU24se power cord. StudioOne is a replacement for it that uses different connectors. The older se is a great cable. No need to spend $1500. 
 

@audphile1 

All jokes aside, going from one sub-$200 cable to another will get you very little ROI if any at all.

Thanks. That's what I figured, and why I felt that the nice advice I got from Audience directly was really just a way to get me into their products but not really likely to change much about what I was hearing. I'm looking at used prices for the model you mentioned, and it's probably something I could do.

Of course, if I aim to put these on the mono blocks, the cost doubles, if I can find two of them.

Perhaps just get one and either try it on my solid state stereo amp? Or on an upstream component, such as the DAC?

Good plan. It will be very nice on your DAC as well.

Why no mention of Audience’s F5 cord? It’s above F3 and below Studio One and is $650.

I’ve tried no Audience cords yet. However, I recently sought cord advice from a dealer who carries all of the gear I use, most of which I purchased from him.

After trying all manner of cord combinations within the Audience line on my exact rig—both at his shop and in many customers’ homes, he recommends an F5 for the Lyngdorf 3400, because he has found that going to a Studio One or higher was not particularly fruitful on the 3400. However, on the Zenith Mk 3, he loves the Studio One.

I’ll bring both cords in for a trial sometime this year. And likely 2-3 other brands to have a shoot-out.

He does not put amps into conditioners, per se.  He uses the Audience box that goes into the duplex and costs about $1200 (I think).  For those concerned about surge protection, he is a big fan of whole-house, which I am looking into.

@hilde45 

'Those who say power cables never matter, please go watch a cute cat video instead of posting here, please".

You mean, like Cat 6, 7 ?