20 Amp Power cable--work with "any" 20 amp unit?

Should work just fine as long as it is the standard 20 amp plug and connector. They should look like this: http://www.uhfmag.com/Images/UHF14-20.jpg. These are 20 amp fittings.

Your power cord may have a 15 amp male plug instead of the one pictured.

As a side note, do you ever notice that many, if not almost all, 20A IEC cords for sale here have 15A ends that attach to the wall? I would suspect that a good 15A Male end to the wall would be as good or as "safe" as a 20A male termination but I would have thought that it would be the standard to ensure that both ends of a 20A power cord would be terminated with 20A ends?

I have to build a DIY cord for a preamp with a 20A IEC and I am hoping that I can cannibalize an existing DIY cord by only having to update the IEC from 15A to 20A...

Well my DIY cord is 12G and my line (12G) is on a 20A breaker and my wall sockets are also 20A so I am covered everywhere other than the 15A termination on the plug end of my DIY cord if I want to follow the UL guidelines/rules.

I guess the "right" and safest way to alter my cord is to acquire 20A terminations for both ends...

No I am pretty sure I got your point but was just saying that if I wanted to be completely lined up I would have everything from the box to the back of the preamp lined up with 20A rated products including the 20A plug for power cord going to the wall which will be the case when my terminations arrive and I swap the ends. No doubt its overkill but it will leave no open issues...

I've always preferred the 20 amp IAC terminal, a much solider connection.