How significant is a power cord upgrade?

Science or snake oil. The jury remains out on esoteric power cables. Ever wonder why the likes of manufacturers such as Krell, Pass Labs, Levinson and others, do not supply esoteric power cords? Makes one wonder in a way. After all what those products cost and few dollars more is of zero consequence to provide a power cable,other than what is usually supplied. Although I use aftermarket power cords myself for amp,preamp and CDP. For me where I live is more of self survival. Seeing as Florida Power & Light continue to struggle with their service after the hurricanes of 2004, and 2005. Power cords I have used is DH Labs, Audioquest,PS Audio and Shunyata. And at times have returned to the cable that came with the unit.

I think to get a good idea of what a power cable is faced with, we need to visit the Nelson Pass white paper on Power Supplies. link below.

http://www.passlabs.com/downloads/articles/powersupply.pdf

In this paper we see the end delivery and what the power cable is actually faced with in certain amplifiers and the components used in those products, such as transformers, capacitors,etc. Interesting reading at the very least.

I'm with Newbee on this as Gnugear specifically asked how significant is it compared to upgrading speaker cords and interconnects?

I too would expect that speaker cords and interconnnects will make much more of a difference than a power cord (after all at least they are in the signal path).

FERRARI, good link.
I have a Pass Labs amplifier and I'll be honest, I have not found earth shattering improvements with an aftermarket power cord with this amp(power cords tried were up to $700).
However, it is not the case with ALL amplifiers and other components. I think the differences you hear or don't hear with upgraded power cords on the amps depend on the power supply design and quality.
For example, a $6 Volex power cord sounds excellent. A Shunyata Taipan Alpha Helix cord does sound just a bit better, but not what you would call a huge difference.
I had several McCormack amps, where an upgraded power cord always made bigger difference than I experienced with the Pass Labs amp. So I don't think that any general rule applies here.
It has to be determined on a specific amp with a specific power cable only by trying.

That being said, I know someone with a Primaluna integrated using a Shunyata Taipan Alpha cord and says it is a very nice improvement.

I take the power cords that come with PCs, put them in the freezer for one month. Then use them. Significant improvement

Interesting, because in my all Krell system, expensive power cables made a BIG difference over the stock cords. I'm happy. ;-) Just experiment and see. I'm glad I did.