Yes.
Honestly, though I think the gauge and shielding of the wire makes more of a difference, though. I'll find out for sure when I compare the cheap Quail group buy Power Cables.
I even saw in increase in power usage listed by my P300 when I switched to the PS Audio xStream PC's on my Amp. It seems that the crappy cables were starving my equipment for power somewhat. Using the xStream PC for the P300 to the mains outlet, is far more subtle, though. But it all helps. The sale was just too good. It almost equaled the cost of building a good DIY power cable, so I bought the xStream cables instead.
-Ed