Everything Matters With Digital

The main things that matter in digital are the source files the ADC that converts and  the DAC that converts. If your DAC isn't up to modern specs in regard to isolation, filtering and reconstruction then these other superfluous items can make a difference  but if everything between works to spec it's not that important. Consider how much time and money you have invested in your internet modem the device that reconstructs the analog to digital signal. So yes everything matters some more so than others. 

Spectrum. If it's digital in and digital out why do you have a modem?

That's what's so hilarious about worrying over freaking cables and switches the signal is no better than what your $100 modem gives you. If you want to know if wires and switches etc.. make a tinker's damn measure the analog out on your DAC or the distorion of your amp and see how much any of it changes with audiophile cables and switches. 

Who decides which half is inferior/mediocre? This in no way disparages the rich audiophile who is impressed with his mediocre jewelry. 

The QAM is sent in an analog carrier wave which is where your MOdualteDEModulate comes in. Yes my ISP is sending me an analog signal which my Modem will modulate to digital that can be read by my network.  Yours might be different if you don't use a DOCSIS based system. 

QAM (quadrature amplitude modulation) signals are comprised of sine waves with varying amplitude and phase shifts, which means even though we call them digital signals, they are actual analog signals carrying digital data.