With AV receivers, different processor settings can make very noticeable differences. And it could be just about any setting, such as exact channel balance or delay times or whatever; if any of that sort of thing is different, you may hear differences. Obviously, more power can make a difference as well, though it depends on whether you need it for your particular speakers. I used to run a receiver that retailed for about $600 and replaced it with one that retails for about $1700 (because I wanted more and newer features), and unless I engage a feature that affects the sound (of which there are many), it sounds the same as before. The newer one can put out about twice as much power as the old one, but the old one was powerful enough to drive my easy to drive speakers to painful volumes with crystal clarity, so more power is not needed in my case.
Also, if you moved any of the speakers when you switched the wires, that could make an audible difference. Or if you moved any furniture.
If any of your connections had come loose or corroded, changing wires could make a difference, without the new wires being in any way superior to the old ones. Or if you had the phase wrong before with one or more of your speakers.
If there is something wrong with your electrical system in your house, a regulated power supply could make a difference, though I doubt that this is actually the case.
Since you are not going to be able to switch back and forth between them very easily, you are not going to be able to do a proper test.