What makes the biggest difference in sound quality?

Everything

Can't really get a more ignorant answer to the OP's question.

It's as if the word "or" is mystifying to someone using the language for decades.

I firmly believe that the right integrated  amp or amp / preamp combo is critical to get the most out of any speaker .    I've had a number of good speakers over the years but why did I tire of them?    Because my electronics were just good....  not great 

I think that's why you see so many speakers for sale .   I finally bought a kick ass preamplifier and honestly it sounded like I got new speakers.   It was profound.

I firmly believe the majority of audiophiles (or audiogoners) don’t read the content of the original post before offering their opinions.  

@nutella

I firmly believe the majority of audiophiles (or audiogoners) don’t read the content of the original post before offering their opinions.

i agree, it is amazing to me when people can evidently type, yet they cannot read...

in some ways it is a pointed commentary on many of the ills of our society in the present day - how people talk past each other, never making an effort to understand what is being asked, what is the exact question or concern being expressed