Power Cord Order of importance

I agree with tvad but i was pretty surprised when i did some PC swaps on my server that there was improvement noted.  It was not with the most high end cord i tried with it that performed best but certain cords on the server definitely improved the digital experience. 

Dac just make sure it’s shielded. No need to spend a fortune. 

Honestly don't think it matters which one, if it is a good power cord it will make the same improvement whether on a DAC, pre-amp, amp, etc. Don't take my word for it, move them around, see what I mean. What does make a difference is if you upgrade your worst PC vs your best. Obviously if you have one that isn't very good it will be a lot easier (cheaper) to hear a big improvement than if you try and improve your best. This will be true regardless of what component it's being used with. 

Put that pre-amp on some Townshend Pods, you will be surprised!

In general, a good quality shielded cord is a good pick for digital source components.

For power amps, it’s current delivery capability that might make a difference.

Otherwise, it’s much harder to predict results with any particular cord. May be little or no difference.

Analog Preamps? Turntables? Most any good quality cord that makes a tight connection is cut out for that job...it’s not that hard.  Shielded cables are still a good idea especially if a low level phono stage is involved. 

Price is never a reliable indicator for many reasons.

In my full analogue set-up the biggest difference was when I put reference level power cord - Purist Dominus ferox- on the power amp, followed by the Dominus on PS Audio regenerator. After that phono stage and preamp - about equal.
Digital is different, so I would not be sure. Might be DAC plus server or DAC plus preamp, and it still might be on monoblocks.
But different components may need different power cords and as such you may have to decide in advance. Some cords work almost equally well anywhere while others don't. Matching power cords and components is not so easy and straightforward if we are talking reference or near reference level.