Making the fixed pc into a migratory cord isn't that difficult... depending on how handy you are. In all, it's a simple task that can be done by an experienced technician... Do be mindful that it may not be seen by another prospective buyer later on as a plus though. Especially if the job isn't nicely done.
you can simply add an IEC connector to the existing power cord and thereby not even open the case by splicing one on.
Another path to allow for sonic changes, and I presume that's the desire here, is to use a simple NEMA to IEC adapter, $3 - $20 DEPENDING.... AND THEN ADD THE INTENDED UPSCALE POWER CORD YOU SEEK TO THE EXISTING ONE via the adapter... NO CUTTING, NO OPENING UP THE CASE. PLUG AND PLAY.
I assure you this last method works. It just ain't the 'audio nut' way.
A good power conditioner also, will allow you to retrieve the benefits of both filtering and the addition of a better cord there too! Plus if the right one is chosen, the advantage of power surge protection too. just a thought.