Power cables for vintage gear?

The lamp cord is only 18 ga. I replaced the lamp cord on the my vintage power amp with 12 ga. DIY cable and it became MUCH more open and dynamic. While doing so, I also added ground out from the amp. This also bring down the noise level.
Hard wire is usually better but IEC allows you to switch different cable and easier to transport the amp without extra wire hanging around.
For more information on power cords, there are plenty of postings for this topic.

As a practice, at the point when the vintage unit requires some servicing ... and most receivers and amps will have to be professionally serviced ... I have the technician upgrade the power cord. I have done this with both my Marantz units ... a 2216B and a 2240. I am not sure if I necessarily have heard audible differences ... but the old power cords do dry out . As for interconnects ... I always have used decent mid level cables and with my vintage equipment it is no different.