I've bought stuff assuming it would sound great and been disappointed (rare, but some recent well regarded speakers failed me), but have also been very surprised here and there...my current fave SE tube amp...some Schiit items...efficient horn speakers...all exceeded my expectations.
How are you hearing no difference?
In my experience, I've never heard two pre-amps that sound exactly the same, nor two DACs that sound the same, nor two amps...etc. Yet, occasionally someone will claim that they heard no difference between Product A and Product B in their system. I find it difficult to believe.