What DAC upgrade made you say “DAMN, that sounds SO MUCH better than my last DAC”?

For me, I went from a Chord Hugo Mk 1, to a Chord Qutest. After 3-4 months I replaced the Qutest with a Denafrips Venus II with a Denafrips Gaia (D to D Converter) using I²S. My system is headphone only, my main amp is an upgraded Woo Audio WA5-LE Mk 1. At the time I purchased the  Denafrips (6 months ago), I replaced all cables that were not already Supra, with Supra Cables, mains cables terminated in Furutech AU connectors.
I have many, many tubes for the WA5-LE (at least 8 pairs each, of high quality, rectifiers, drivers and 300-B's).
Headphones are Sennheiser HD600, HD650, HD800S, Focal Elears, Audeze LCD-X's and Meze Empyreans.
The Qutest was very good, but the Denafrips made everything disappear, it just leaves the music!  My only regret is that maybe I should have gone for the Denafrips Terminator-Plus, but I'll never know since I can't audition it!

Audio Mirror Tubadour III SE I saw a very clear and substantial improvement, all other things in my system being equal.  Later I bought a PS Audio DirectStream Sr. DAC, it wasn’t as bright an improvement but it is clearly a better sounding DAC - in my system.

I heard the antiquated Philips TDA1540 chip with the Tube Output. It didn't rock my world when I heard it at my friends place. We did a head to head with my PS Audio DSSr. Tubadour III SE sounded thinner by comparison.

Tried a bunch of DAC's but my search for a DAC stopped after I put the Sonnet Morpheus in my system. 

It’s been fun reading all of the posts as I just finished up a many month DAC hunt. 
I tried dCS (Bartok and Rossini, both with and without the Rossini Clock), Brinkmann Nyquist Mk II, Nagra Classic, and Berkeley Audio Design (do not remember which one), but the only DAC that got me excited moving up from my Bluesound Node 2i was the MSB Premier with Powerbase, v2 renderer, and femto 93 clock. The timbre I’m hearing now is exceptionally natural and the imaging is very 3D. I’m not going anywhere DAC wise until I can afford a Reference. The other DACs were all very nice, with the Nyquist Mk II my second favorite overall, but the Premier really stood separate from the rest. 
Now, my Shunyata Everest/Omega XC combo and everything else in my system certainly helps the sound, so maybe the overall combination is really what made me go “wow.” I’m getting a very compelling musical experience every time I sit down to listen, day or night. 
Happy listening!

I've owned a PS Audio DirectStream DAC since they first came out, and every time I've applied a firmware update, I've enjoyed better sound quality, the latest one is one of the best upgrades they've offered.