I’m also worried about how much of the harmonics in the music is LOST by the amp?

The sort of fine detail you are talking about is lost everywhere. From the panel through the power supplies, from the platter to the phono stage, from the amp through the crossovers and internal wires and speaker cabinet and drivers. Every tiny little bit of it. For some reason people want to focus on amp. Or speakers. Or what was the latest one? Oh yeah, stylus. The stylus is the most important. Didn't you know?

Meanwhile, where was it I saw that one guy, everything matters? https://systems.audiogon.com/systems/8367 Right. That's the one. Everything matters. Including, yes, even the amp.   

You can hear it easily. Play your favorite music. Flip off your circuit breakers. Play it again. Hear that? That was just one little bit. Imagine getting rid of that, times 100. https://youtu.be/zZcZ6eJoxeE?t=1

ChiFi...Garage Boom Boxes....Cable Lifters....Magic Dots....Meh!

Every link in an audio signal chain plays its part, however, it is an irrefutable truth that what is lost at source cannot be recovered downstream, Ergo that Rock on a Stick is of no little importance.

Get a great amp not some junk.