You probably mistook one thing. "There is no difference in quality from a 100$ amp to a $1000 amp" was surely written somewhere and is probably a punch-post. One that marks you. But I believe this is wrong, because 100$ amps are really different in the quality when compared to a 1'000$ amp.
And whatever quality you go, you will generally have different feel and finitions on a 4'000$ amp than on a 600$ one.
BUT
If the amp was made ok (good filtering, good layout, serious component), you will have difficulties to
hear any improvement at all between a 800$ or a 3000$ amplifier. The expectation bias will be higher on a high priced amp, you will really feel the need to hear more of everything. But in fact, amps are amps. They amplify a signal, and the best way to do is go for a neutral way.
Please, don't misunderstand me on that. Some speakers are demanding ones, and it's important to have an amp that can feed the type of speaker you will have on them. So they can perform to their best. But, if we are speaking about an uncritical/undemanding speaker in power and impedance, even some very normal amp will do the job.
Certainly, some have more K2 harmonic distortion for a slighly softer and hotter sound, others are completely dry for letting the things like they was meant to be reproduced. But this will be, for the maximum, "a feel". Not a significant difference. A lot of peoples are puzzled when it comes to recognize different amps when the blindtest method is used. Simply because the differences are so tiny that our own perception vary on more average levels that the amps themselves. So you could spend your money on a 1'000$ Abrahamsen and be absolutely sure to have a great amp. You could spend a little more on an Audia and have the same quality of sound, but a different feel and lookl. Or you could go for an Accuphase or Luxman, that will sound really close, but with a different charm and feel as well.
If money is short, and the speakers uncritical, keep the fees on the amp short. If passion and dedication to your hobbie are important, go for the most beautiful you want to afford.
If you want some facts, you can refere to
this post I made before (I put some mesures on that).
(I tried to let my example be simple to understand, please note that I didn't spoke about different amplifiers classes or types like tubes or A classes, that have "specialities" that makes them different. I focused myself on class AB and H amps)