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

Reference speakers are on average starting at $15-$20 k for a decent true reference speaker on Average considering today $50k is  the mid high end range  for a speaker, there are a few exceptions to the Rule.
one key is a solid cabinet , High quality drivers , and premium Xover
components. Many companies use $30 tweeters and that’s ok for a under $5 k 
speaker ,name brand such as Accuton, Scanspeak ,Seas ,in their upper range are premium and more $$ costly but, much lower in THD . Speakers sold direct 
like Spatial Audio labs ,made in U.S.A  open baffle speaker but in the X series 
all drivers are premium especially the custom Beyma AMT tweeter- upper midband  and under $10 k a steal beating  many speakers  2x+ Their cost.

Quads excel In the  mid range especially the older 57, but not in Bass or highs vs $$ speakers 
maggis I have owned a bunch cheap Xover parts,and frame is a disaster unless you buy a quality Mye stand  they flex like a sail
I am referring reference in a 3 way capacity when I am saying a retail speaker $15-20 k is average for a mid fi reference speaker 
by today’s $$ pricing standards when $100 k is considered upper end ,$50k mid reference ,which I cannot afford.sadly .