I need advice for power cords

In my system there are 4 components that power cords are interchangeable.  They are PrimaLuna EVO 100 Tube Preamplifier, PrimaLuna EVO 100 Tube DAC, Manley Chinook phonostage and Dayton Audio sa1000 subwoofer amplifier.   Should they all be upgraded, if not all which one to change to give me the most improvements.  I can't go crazy on cost, 1k to spend.   I've followed along with many threads on this subject. Always looking to make improvements to sound quality.   Many of you have much more experience with cables than I do so what do you recommend and I can do the research.  On a side note my McIntosh MC75's are vintage so old thin manufacturer cables and probably shouldn't change them. 

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Upgrading the house wiring is the best you can do for your equipment. 1. separate phase (if you have 3 phase system)

You mean 3 phase elect, or 3 phases of something else? Lost me there.
Who has 3 phase elect. not many at all, ay. Single phase 220-240.

Voltage maintainers, and cleaners go a long way, NOT SURGE Protectors, useless, to maintain voltage..1000.00 wow, go a long
way with that, in materials. You can talk to a GOOD electrician for
about a thousand dollars... Really!!! No work though..LOL

In Europe you can have single phase or a 3-phase electrical system in your house (eg 1x230V at 35A or 3 taps of 230 V 25A). You can use 1 phase separate for your equipment and the other 2 for your all your other groups in your house. There will be no contamination from leds, dishwashers, microwaves, phone chargers etc..). If you have a oscilloscope you can check for the best phase with the least of noise from your neighbors. (I checked it at my listening hours)

If you want to do more, you can also put another earth rod in the ground for your audio system. There are some audio shops that provide this kind of service. I am an electrician myself and I worked at a cable company as a (test)engineer and I have some equipment at home (I am not on the level of a brilliant designer like Bruno Putzeys or Nelson Pass) but I understand the importance of low R,L,C values and a good foundation for your equipment. Tightening your screws and using contact enhancers is also a simple and good tweak to start with.
Try Pangea power cables at Audio Advisor. Very reasonable price. I use them with Spectral mono blocks and Spectral preamp. I am satisfied with the results.
In my experience after ripping out drywall for ceilings and walls running 4 dedicated lines  to a sub breaker box, my issues actually worsened.  

The AC power was that dirty in my house - in part from my own computers and electronics and in part from the regional grid - neighbors switch power supplies, etc.

This noise does travel retrograde.

Solution:  TORUS Power isolation transformer - I placed a 75A wall mount unit.   For those considering one and use tube amplifiers purchase a unit rated for 4x the measured power draw of your amplifiers.  If you system draws 10A, then a 40A unit would be appropriate.  

The other consideration is RF/EF radiation from LED lights and dimmer switches.  The dimmer switches (which function by rapid cycling current) create horrible AC noise that I measured polluting my dedicated lines.
I have a Primaluna HP integrated, and the Chinook.  I put Signal Cables PCs on them.  The improvement is subtle at best.   They weren't expensive, so I'm keeping them.  I did notice a bit more dynamics to the sound, but again, subtle.  I'm not convinced it would be much different if I spent $1k or even $10k on a PC.  Consider your overall system and the value it will add overall.  The Signal Cables were under $100 each.

As others have said, I'd start with the PL and Manley, and if you have a power conditioner, that too.  But, I don't see spending multiple hundreds on six feet of wire.