How much does power amplifier really matter comparing to other hi-fi components?

     Every component shares a slice of responsibility, when it comes to accurate sound reproduction (not to mention: room treatment).

     ie: Picture all of your components (sources, cables, pre/power amps and speakers) as panes of glass, through which you want to observe something living.

      The accuracy/enjoyment of your observations will be determined by how many and how dirty the panes.

       How critical you are as listener, will determine your level of involvement and investment.

I believe it’s a good percentage of your system and should be chosen per your speakers and their capacity. Don’t forget your power conditioner and monitor. I spent 500$ on one that insures it’s protection. 

Everything matters. Amp matters a lot. Recently I’ve owned 3 amps I can swap among in my system. Each has a very distinct sound. All 3 are way more than enough power (120 - 275 Watts / ch) for my 96dB Tannoys, so overhead & drive capabilities are not really a variable. I’m even writing down particular combinations of cartridge & amp that work best together lol.

You didn’t specify your budget!  I can’t believe all these people made recommendations without that info.  It matters because up to a certain level, you’d be better off with an integrated vs. separate power and pre.  An integrated will compromise on the preamp section, but save $ on an interconnect.

I would think speakers would have the biggest impact.  I also think a pair of REL's make a huge difference, especially a lower listening volumes.