power cord too short? what now?

Hi, yes there is no question you will lose some benefits of adding an extension to the power cord. I have found it is far better to invest in a longer length to make it redundant for future applications.

Buy a longer cord and refrain from adding an extension cord. What kind of PC is it?

This should do the trick.

Buy a longer one?

In the past, I have posted that the very top of the line Mapleshade Records power strip does not degrade sound, but actually seems to very impressively enhance power transfer as judged by the audible improvement.
There are even other extension cord-power strips favorably mentioned in past postings by Audiogon members, one of which you might choose, instead.
Still, it might be simpler to replace with a longer length of what you feel has already proven to be synergistic with your system. Then, your redundant power cord can be put up for sale.