Jedinite,
I once built custom one from VanDenHul leftover bulk that they sent me for $25 shipped 6' total length that I plugged into modded VTL-MB100 that used to have fixed(non-detachable) power cord. Playing with non-detachable power cords did not bring to my ears any difference, but certainly increased the value of the modded VTL when I sold it:-).
Certainly playing with detachable ones is more fun, but to my practical experience the fixed ones especially for audio applications make much more sense to me (less connections, less transients, lessnoise) hence I did not bother to cut chassis to install IEC recepticle.
When I removed the stock power cord I was amazed that the wires looked brand new after nearly 16 years of usage and in addition it was very well designed. Still keep them in case anyone interested to buy:-) Alais from the aftermarket wires that covered with fancy hoisery and sleeves, I had a chance to look under the stock one and hence made my conclusion about ROI.
So folks, learn what you've already got before going crazy and stretch your pockets.