Power cord - 5 ft vs 10 ft ?

If you are using a high end power cord, then 2 meters is the preferred length.

I had never considered length until recently. I always thought short to avoid clutter. My audio guy had told me 2. Meter was optimal. I happened to have a one meter and two meter of the same coed. I tried them both, and lo and behold he was right, the two meter sounded better. He had said, “You get more conditioning”. Well, after fifty years at this, I am still learning things.

Theoretically, since all power cords have a resistance per foot, the ideal length would be as short as practical. If by 'performance' you mean as low of a voltage drop to the amp as possible. 

@jasonbourne52 I can move my amp to be one inch from the outlet. Any idea where I can get a 1” power cord? Or should I just hardwire the amp to wall?

@jumia you’re overthinking it. Here’s why….a 1m AudioQuest Hurricane will be way better than a 3m AudioQuest Thunder for nearly the same price. Get where I’m going with it? Quality over quantity. Unless money is no object. 

For power cables my understanding and experience suggests that shorter is not better. Depending on cable, at least for the ones i use, 1,5m-2m is perfect.

Short as comfortable.  Using shielded will ensure you have the best noise blocking (both in and out). 

There is something to be said about using a longer shielded cable.  A little R and C can help reduce noise, but by a tiny amount.