Why Expensive power Cables when Romex behind Wall?

I was skeptical too... had some "pretty good" power cords that were made for me by a local cable deigner; better than stock cords but certainly not current state of the art. I had heard them compared to stock cords and could CLEARLY hear an improvement. That was 7 or 8 years ago. I have upgraded components since then, and got the system settled down... then began to audition new power cords. Some were no better, some were worse (even expensive ones). The ones that I settled on were again, clearly better in my system. It doesn't make scientific sense to me, but it happens. I tried making a bunch of PCs. I used romex all the way to the component; hard and hashy sounding. I tried a few different kinds of braided wire too; conclusion, this guy cannot make a PC that sounds as good as what the Power Cord magicians are making. Go figure? MG

This is an excellent question but that 6 foot high-end power cord can make an audible improvement. This similar to using high-end speaker cables. Most internal speaker wiring is tin-plated copper yet one can hear an improvement. There are many claims of how power cords achieve this sonic improvement by filtering, shielding, and lower inductance. Of course there are many so called high-end cords that make no improvement at all (IMO) so be careful in your selection.

"Hospital" grade sais it all. Would you feel safe, if the high tech respirator keeping you alive had a lamp cord and was plugged into a $5 power strip from Walmart? Hospital gear comes with big fat cords and plugs (plus conditioning) because they don't dare skip a beat (no pun intended).

Your gear won't skip a musical beat either.

Even though the cord is short, it still contributes to the overall inductance. ROMEX has up to 10 times the inductance of good after market power cords. If the the last 6 feet of a 20 foot run to the panel is an after-market cord, it will add very little to the inductance of the first 14 feet.

Systems reproduce upstream content using upstream power sources (except some battery powered phono pre-amps). In that regard we spend ridiculous amounts of money. But our systems are (hopefully) designed to do the best job possible with the presented content and power source. So we spend our money to minimize changing, or losing, the content and to doing the best it can using the power available. But I'm in the camp which says that with my upmarket equipment the equipment designers have designed their equipment based on the known vagries of the power source (one of the design decisions requires overspec-ed transformers for example). So what the hell. Let the equipment do the job it's designed to do.

Having said that I've upgraded my PCs ! Just in case. If nothing else I get a better connection to the romex. Sad really.