Where do cables upgrades have the most impact?


Assuming all existing cables in a system are atleast mid-grade (not junk), which cables/interconnects should be upgrade first and in what order? Where should one start?
128x1281extreme
Curious if those saying the power cable had the most impact are plugging into a power conditioner or a wall outlet?
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Looks likes theres no consensus . Best bet is to buy a cable and try it out on all your components . 
Factors that tend to increase the criticality of speaker cables:

-- Low speaker impedance.
-- Long cable length.

Factors that tend to increase the criticality of line-level analog interconnect cables:

-- High output impedance of the component driving the cable.
-- Use of unbalanced interconnections.
-- Long cable length.

Factors that tend to increase the criticality of power cords:

-- The component being powered has an unregulated power supply and draws large amounts of current that fluctuate widely. Namely most power amplifiers and integrated amplifiers.
-- The component being powered tends to generate significant amounts of electrical noise, that may couple via the power cord to other components. Namely power amplifiers, integrated amplifiers, and digital sources.
-- AC line voltage at the particular location that is lower than nominal. ("Nominal" being 120 volts in the USA).

Phono cables and digital interconnect cables involve complex issues that I won’t address in this post, but their criticality will vary widely depending on the specific equipment that is involved.

Regards,
-- Al