I had no real experience with power cord/cable upgrades until the past year. I use a PC for both my video (blu-ray) and audio source, so my go to to test things was using it on my PC first, and there is certainly a difference, enough so where I upgraded every power cable in my video chains (.
Since my hobby started years ago through video and not audio my conclusion in terms of video cables has come down to low wire gauge and silver as the conductor leads to the best effect (of course there are other things to consider such as conductor purity, conductor geometry, and dielectric as they all do not look the same in terms of output) and so far it seems like this is the same case in terms of power cables where silver offers a more airy three dimensional space, brighter image, better color reproduction and separation, and clearer details. The 10 gauge silver power cables are a bit better than the 12 gauge ones I've used, they just seem to have an enhanced version of a similar effect (just to note Cabledyne just had a 50% off sale on their 12 gauge silver power cables that meant $87 for the 1 meter version, though the sale just ended they are doing something for Cyber Monday, and I'd assuming the sale just ending this past week means a better sale on Cyber Monday). I just got done testing seven different power cables on my PC back to back (then doing that again just to make sure everything checked out on the second pass), going through the same video and audio tracks and viewing the same still images on each and each has a bit of a different signature. My desktop background (left over from Halloween) looked different with each cable. It's the same with a tv/monitor (and I'll safely assume projector), a video scaler, a signal amplifier, and cable box.
I can tell you there's a good difference between the first power cables I tried a little over a year ago in Pangea AC-14 SE's and others I bought after. The AC14-SE was a good amount weaker than one I bought from a seller on eBay by the name of BLE Design for $17 less than the $50 Pangea (BLE cable: good cable, the iec end on the cables is thin and chintzy though- mine cracked, but performance holds up compared to far more expensive cables), The BLE cable is advertised as using 5n copper in a 10 gauge cable with red copper plugs. There may not be a huge difference once you find a good upgrade cable compared to other power cables in that class and above as at a certain performance or price point and up there seems to be very good care going into the cables, but there are differences. Once you find a sweet spot it's up to you if a small yet still discernible upgrade may be worth your money.
I've even noticed that coupling a good cable to a weaker built in cable or power supply that a tv has works as well (did this for my Loewe Aconda, would love to have a technician upgrade the entire cord from the inside though). It's unfortunate that some hdtv's now have a thin little bit of cabling going to a power brick that has a c7 female connector though, as it'd be better to not have to couple a good cable (potentially to a c17 to c7 adapter) to a brick that then connects to a thin wire to the tv, instead of just having the cable connecting directly into the tv.
I cannot tell you the reasons why the cable upgrades work, I honestly thought the power cable upgrade thing was a bit silly until I actually decided to try it just in case there was anything to it, but it makes a difference. Mind you my eyes have been attuned to discern video upgrades for around 20 years now to the point where I can pinpoint what cable is being used in a blind test, and blue eyes are better at capturing light, so I can only attest to what have seen and cannot say others will experience the effect at the same level, but I am sure once you find a good cable/cord you will see a difference. With so many different a/v-phile level cables out there I cannot tell you which ones are right for the job and which ones may be "decent but not at the level you'd be truly happy" like the Pangea was for me, so you may want to audition a few or look for some respected ones used.
