I’m not an engineer, but my uneducated guess is that the harder the speaker is to drive the more the amp matters in terms of sound quality. My speakers are a relatively easy load and I hear bigger differences between preamps than amps, which would echo what others have said that “it depends.” In the end, and no matter which one makes a bigger difference in a given system, balance is the key and that the amp and pre compliment each other in ultimately achieving the desired sonic characteristics. That’s my take/experience anyway.
