Comparing a Yamaha s301bl to a rega elicit mk5 - a/b on some paradigm 800fs and they sound the exact same. Looking at the specs it makes sense - I don’t know why I’d ever use the full wattage of even the Yamaha without getting hearing damage and the THD being 0.019% vs 0.004% makes no functional difference. Are high end amps the new snake oil? What exactly are you getting for 10x the price here (besides the rega having less features and the rega brand name?)
if you cant hear the difference, the component that you replaced was not the weak point. Either your speakers, your connects, or your room itself will not allow the superior amp to shine. If you are happy with what you have, awesome, congrats. If you are not happy and that is why you are looking at upgrading, I would look at the other items I mentioned and leave the amp for later when you figure out the choke point.