For a second there I thought this was one of those April Fool's postings, but soon realized that it's already April 22nd. Seriously?? Power cord length??
Let's see: the power generating plant is probably hundreds if not thousands of miles from your amp, the local sub-station definitely a few tens of miles, the wiring from the transformer in your street to the outlet probably a few hundred feet ... and you are worried, and people are seriously discussing, power cord length? And after you connect the power cord, you still have to deal with all that pesky wire in the primary and secondary of the power transformer, which is just the size and length required by the amp.
So, the experienced and very knowledgeable electrical engineers at Krell build a $40,000 amp and it comes with a power cord that they tested and know it is absolutely perfect for the amp. Then some sales rep from an audiophile cable company tells you: they're idiots. Use my $10,000 power cord!! (which is mot likely worse than the one Krell sent you, and probably a fire hazard). I'm an electrical engineer and this whole discussion of cables and specially power cords and power connectors really insults my intelligence.
Let's say you're in a Supercar forum and just bought a Bugatti Veyron. There is a company, or someone in the forum, claiming that you should ditch the original fuel line from the gas tank to the engine and buy their improved super duper fuel line for just $60,000. They claim that will make the engine run smoother and you will feel the improvement in the horse power of the engine. Pretty ludicrous, isn't it?
Just use the power cord that came with your amp.