Radine, I know you're only being friendly and helpful, and if I've not made it obvious I'll try to re-phrase...
1. I've spent a lot f money on the speakers, and if think my system sounds fantastic.
2. Others find they are noticing quite significant benefits to using better DACs and pre-amps compared to lesser ones. I don't find this.
3. I therefore come to the conclusion that one of the following holds true:
A. I (and others who have heard my system) are cloth eared.
B. Something about my setup (room, supports, leccy supply etc. etc.) is holding my sound back to a level where I'm stuck at the lowest common denominator.
C. My method of appraisal is wrong, and with long term relaxed listening the benefits of the better kit becomes apparent.
D. Other folk are in some way deluded. Expectation bias (or whatever) has messed with their heads and there is no actual difference between DACs/pre-amps.
State X == A. or D. are true. I can sell my Young DAC and TEAD Vibe and spend the money elsewhere.
State Y == B. or C. are true. Relax/fix the system issue, and enjoy better sounds.
I simply want to achieve state X or Y with enough personal certainty to make the correct sell/don't sell decision.