So far from reading this thread, sounds like there is money that could be made here....
A simple cable support bracket that does not connect directly to the equipment and does not harm or damage the equipment or after market PC in any way.....
Seems to me in the case of power amps and preamps, even some CDPs,... the weight of the equipment coupled with leverage could be used to support and hold a cable support bracket in place.
The support bracket could be made from steel or aluminum.
One end of the support bracket would have a flat surface, say about, 2" wide and around 6" to 8" in length. This end of the support would fit under the audio equipment. This part of the support bracket would have a heat resistant rubber covering to protect the bottom of the equipment as well as the platform or audio stand shelf from any chance of damage. (Maybe simply heat shrink tubing)
The other end of the support would be narrower, say around 1" to 1 1/4" wide, and would extent outward from the back of the audio equipment for the cable support.
Some type of height adjustment would have to be incorporated into this part of the support bracket for proper cord IEC connector/equipment alignment. If made of steel maybe just firmly bending shaping the bracket.
To protect the PC from damage a soft material covered cradle support for the cable to rest on. (Maybe cover the entire support bracket with heat shrink tubing)
A simple 1" or 1 1/2" wide Velcro strap could be used to hold the PC to the cable support cradle.