What does anyone think of standard IEC Mains Power Cable upgrades. ...
Rach'
It depends on what you mean by "upgrade". Do you have a specific cable in mind, and can you provide a link to the cable?
In nice round numbers, a 100w/ch amp can have 45v applied to the Amps and consume about 5 amps at the speaker terminals. But that passed through a step down transformer in the power supply. So working backwards, that 45v and 5 amps on the speaker terminals is 240v and 0.9375 amps at the electrical outlet. That is the peak current for a full 200 watts from a 100w/ch amp sustaining full power. Likely in common use, the current is more like 0.042 amps.
So a common 14ga Power Cable, which peaks at about 20 amp, but typically has a 15 amps rating in an external plug-in cord, is only commonly using about 0.28% of its capacity.
Many fancy Power Cords are shield, 1 meter of shielded cable is of limited value when it is connected to miles of unshielded Power Grid.
Now you are free to want some nice fancy
LOOKING Cables, that is certainly your choice, but know that appearance is all that you are buying.
Yes, there are certainly a group of people who claim that Fancy Power Cords can effect the sound quality. Unfortunately none of them can come up with a logical explanation as to why. Most amps and other similar products have heavily Regulated Power Supplies, and that assures the final Power Supply Voltage is fixed and stable within a very wide range of power demands.
In fact, it would not be uncommon for a 200w (100w/ch) Stereo Amp to actually have a 300w Power Supply, so it has considerable reserves.
As mentioned by someone else, in worst case scenarios, it is possible for the Electrical Grid Voltage to be low, or other aspects like noise to come into play, but a Power Cable can not effect any of these things.
Yes, you are right to want a good quality, nice looking, durable cable, but that can be done for very modest money. And I suspect if equipment manufacturers were not supplying adequate Power Cords with their systems, Health and Safety would shut them down pretty quickly.
Yes, a new Power Cord does make some limited sense ... up to a point... but understand what you are getting and why.
Steve/bluewizard