No dobut some differences are not real, mood and how much attention you are paying are under rated factors for most people. As a rule remove all 'tweeks' (including expensive cables) from you system once a year and add them back sequentialy as a test. Another question you have to ask yourself is what percentage of the differences audiophiles claim to hear are improvements? I have really gone through a few systems changes recently that while they got me listening since things clearly sounded different the changes were not 'better' after longer term listening.
