I think 4 ft is standard. I personally use 5 ft "boutique" power cords as that’s the length which they are commonly offered. 6 ft and above are usually for special applications. Are you able to shift the equipment or rack so as the length of the cords will fit? That’s what I do most of the time. Excess cable length is not good and troublesome to maintain. It’s not good to have the cables(power cords, speaker cables and interconnects) touch each other.
If you need 8 to 10 ft cords, I suppose you would be able to buy one which costs below $50 which may well offer comparable if not better performance than the standard cord which comes together with your amp?
