I’m gob smacked. What were you’re aha moments?

Listening to Chet baker self titled out of Devore Orangutans 0/93
and audio research gear

Two recent moments.
Swapped stock fuses in my Parasound Halo A21 with Hifi Tuning Supreme units.

Set up a pair of 6" GIK Impression Regular panels at first reflection points on back wall, another pair on first reflection points on side walls, and one narrow panel in each of four corners.

When I got rid of my Preamp and dac and got a direct stream dac/ preamp from PS audio. It was like holy crap what the F just happened. How can one piece of equipment make such a difference?

My B&W 802N speakers finally sounded perfect. Silky smooth highs and mids with plenty of base that was lacking previously. 

Switching from NAD M51 Dac (very good) to an Audio Note 3.1. A week later I changed out the Bryston 1b pre for a Audio Note M3 line pre.

Just another level I guess. 

@Imnop, What prompted you to replace your Oppo UDP-205? We have (had) very similar systems. I have UDP-205, integrated (Pass Labs instead of Anthem) and ML Montis.  My main reason for getting the Oppo was the combination of transport and dac w/balanced outputs.  What are you using for a dac now?  To get on topic, my biggest and first "aha" moment occurred in high school early 70's.  I was looking to get some cheap department store all in one.  Guys I worked with hooked me up instead with AR-XA table, Kenwood integrated and Advents.  Hooked from then on.  The next was getting Infinity IRS Gamma.  Would not have sold them except for reliability issues.