If one does not have the 20 amp dedicated line it will affect the signal. Outlets, power conditioning, power cables, audio stands, isolation devices and of cause room acoustics. After that front end, ICs, amplification, speakers cables and finally speakers and your listening position. Another important thing is the synergy between all components. Great cables like Nordost V2 will sound great with speakers like Sonus Faber, but may be too much for speakers like Magico that is great with Shunyata or Audioquest cables. The same with amplifier and everything else.
But if integrated or pre/amplifier combo does not have enough current to drive medium /lower efficient speakers - even if those speakers are great ones and cost like a good car, one will never hear proper drum kicks, 3d soundstage, bass and other important things. If amplifier does have a lot of current but speaker cables unable to deliver it to the speakers - again you will never hear full potential of your amplifier and speakers.
I can go on. For the last 15 years, I spent well above $100k to have sound that I think gets me closer to jazz live music, but my whole system costs around $65k retail. Were did other $100k went - trials end errors and lack of understanding that everything is very important in the system. And another very important thing - no matter how good your dealers are, no matter how great reviews and users opinions on specific components - one have to trust his own eras only.