Cable differences -- power, interconnect, digital, and in what order?

@hilde45 yes I did - digital and ethernet cables make a difference but they don’t have the same impact as other cables. Think about it…your amp is the last link in the chain before your speakers. Interconnects between your preamp and amp will impact the sound much more than anything upstream including digital and ethernet. Now you need to remove your next bottleneck - speaker cables. And feed the amp good power. 
Now here’s the caveat though…by doing the above you’ll expose other weaknesses upstream starting with your source to preamp cables. Your digital cables aren’t in the picture yet. And if you have a power conditioner for your sources, the power cord feeding it will be next on the list. Then the power cords for sources, then the digital links at the very end. 
Just my thoughts based on my experience. And…it depends on many factors that can change the approach so YMMV as we love to say here.

@hilde45 I’m going to make an assumption you are an experienced listener, your components, speakers and room are on the level to resolve changes in components or cables.
So in my experience…

1. Interconnects

2. Speaker cables (super close second to ICs)

3. Power cables

4. Digital cables

5. Ethernet cables

As to the component to start with on a power cord upgrade? I’d say amplifier first, then power conditioner for your sources, then sources(turntable being very last and I would just use a good stock cord). 
 

@hilde45 correct. And to add to the power cord conversation…not all power cords work equally well on all components. The only exception I found so far is the Audience AU24se power cable that worked very well on all 3 DACs that I had over the last 1-2 years. It wasn’t great on amplifiers or preamps. I’ve also had power cords that worked great on one amp and not as well on other amps. It’s all about trying and finding what works best.

@decooney is the power cable on RG of equal or better quality than the power cables on your source and preamp?
As to answering your question…I would try it and determine where it works best. I would also try to see what it sounds like with the higher end cord on preamp direct into wall outlet bypassing the power conditioner, especially if you have a dedicated line. Probably not the answer you were looking for, but there’s really no substitute for a listening test. 

After I ran two dedicated lines, I actually prefer the sound of my Pass XP22 preamp when connected direct to outlet. It wasn’t the case prior to implementing the dedicated circuits.