I used to use an array of heavy gauge 20 amp Belden power cords that I made up myself from a 100m drum that I managed to get via a client. It's the same stuff that Krell supply (or used to supply) with their amplifiers (none of which I ever owned myself) so I figured it was a pretty safe bet and I used it for many years. But, once I started using Bryston amp's, I found myself forever trying to eliminate a nasty transistory edge to the upper registers.
Eventually, after much frustrating and protracted experimentation with every other power cord I could lay my hands on, I decided to try the stock cord that Bryston supply with their amplifiers (why it didn't occur to me just to start with those I really don't know). For some reason, the first component I plugged the Bryston-supplied cord into was my Wadia CD transport and hey, presto that made a surprisingly positive difference.
The next logical step was to use the two others I had with my Bryston 7B-SST's and that produced further noticeable improvements. Progress at last.
The other three Bryston components in my system are the BP26 pre-amp (bought pre-owned without its stock power cord), a BDA-1 D:AC (which comes with a much lighter weight cord of different provenance, though as it's what's in the box I guess it must be okay) and a 10B SUB crossover (the cord from which is presently assigned to the CD transport).
So, if I'm to have the same power cords for every component in the system (which seems like a good idea) I needed to source a supplier of those 2.5m Mega Electronics cords (HO5VV-F 3G) that come with the Bryston amp's. This I've managed to do by way of Major Electronix in Ohio, who sell them for just $5.81 apiece, so I've ordered three (with an extra one for my Lyngdorf SDA-2175 power amp driving the sub's) which, as I write, are on their way, though there'll probably be a bit of delay whilst they clear UK customs.
As a friend suggested quite some time ago, when it comes to interconnects, speaker cables and power cords the surest recipe for good results is to use what the manufacturer recommends, the logic of which is unassailable. If Bryston weren't happy with the way their amp's sound using these Mega Electronics power cords, they wouldn't include them as standard. They certainly have to be the benchmark against which to judge any other alternatives.
So that's my take on the subject.