A slightly different (or even more than slightly different) sound from each speaker is normal, in the sense that each speaker's immediate acoustic environment is distinctly unique, despite all the speakers being set up in the same room, due to their different positions within that room, and the fact that almost all rooms and furnishings are asymmetrically laid out to a greater or lesser degree.
But a different sound from each channel of a stereo amp being regarded as 'normal'? Shouldn't be. If the amp is working properly, each channel should sound indistinguishable from the other. To test if your electronics or speakers are actually playing are part in this, or whether it's just what I described above, you should also try swapping the speakers side for side and listen for what, if anything, sounds different.
If the only difference attributable to the electronics really boils down to the noise floor, and you can't hear this from the listening position, then don't worry about it. And remember, when you do any of the listening tests, make sure you're auditioning a monophonic program signal (and if you haven't been, all bets are off you my friend :-)
But a different sound from each channel of a stereo amp being regarded as 'normal'? Shouldn't be. If the amp is working properly, each channel should sound indistinguishable from the other. To test if your electronics or speakers are actually playing are part in this, or whether it's just what I described above, you should also try swapping the speakers side for side and listen for what, if anything, sounds different.
If the only difference attributable to the electronics really boils down to the noise floor, and you can't hear this from the listening position, then don't worry about it. And remember, when you do any of the listening tests, make sure you're auditioning a monophonic program signal (and if you haven't been, all bets are off you my friend :-)