I never risk a recommendation to a power cable - I have found that they are extremely depend of system. Some people look for "magic" in power cables, I find them "witchcraft" I can't understand at all.
Its all about Voltage drop across the power cord (or wall wiring). Some products, especially large tube amps, are sensitive to the line Voltage since they get a double whammy when it goes down: the B+ drops but perhaps more importantly the filaments cool off, lowering transconductance. To you get reduced power, increased distortion and increased output impedance.
Its both measurable and audible. I've seen power cords rob an amp of over 25% of its full power.
Large solid state amps, particularly those with class A or 'enriched' (a marketing term) AB operation are also line sensitive, although less so than tube amps and by quite a lot, since they usually employ feedback, which allows the amp, to a certain degree, to reject that which is not the signal.
The Voltage drop can also manifest as current limiting at high frequencies, since in most cases, there is a power transformer, rectifiers and filter capacitors in the power supplies of the amp. Since the rectifiers only conduct when the filter cap Voltage is less than that of the power transformer feeding the rectifier, and since the caps retain most of their charge between iterations of the line frequency, current only flows at the peaks of the AC waveform. Sometimes this might be for a fraction of a millisecond. If the cord lacks bandwidth, the current pulse will be curtailed.
An excellent power cord can be constructed (here in the US) using good quality IEC connectors, AC plugs and electric stove or drier power cord, the latter of which can be had at Menard's, Lowe's or whatever passes for that in the neighborhood; low Voltage drop and good high frequency characteristics.