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

For the OP, no one has mentioned the front end, as a matter of fact yes, some have reported changing the server made most of the impact and I believe what they are experiencing

I have tried a project S2, rme adi-2, Denafrips terminator, holo may, all these dacs with a front end up sampler running HQPlayer
The biggest change in my system have been hqplayer, not the actual dac, good dacs will have differences with others but if your front end is crappy and noisy there is where a dac will excel over another and there will be wider differences between them, when the front end is good the Dac gap narrows

Maybe not  what you or others want to hear but it is my experience.

Just asking. @luisma31, what is a front end upsampler and HQPlayer? The streamer or transport? 

Hqplayer is an app that runs on a PC, can be under windows or Linux in headless mode. It is not a streamer you can say it transports the audio but conceptually I see it differently.

When you send audio to a dac the Dac uses internal upsampling and digital to digital and digital to analog reconstruction filters for the entire digital to analog conversion. Obviously the Dac executes this conversion with simple mathematical operations and IIR and/or FIR filters.

If instead of sending audio to the Dac you send it to a computer first to be pre processed by a high speed Intel or AMD processor with more complex filters and operations doing the heavy lifting of conversion and passing near perfect digital audio afterwards to the Dac for final conversion the results in my opinion and others are outstanding.

So it does digital to digital conversion passing the result in DSD or PCM format to the Dac.

I don’t like this analogy but If you are familiar with Chord it does kind of the function of the Mscaler.

I have friends that conceptually never even tried it because they say it add colorations, I have other friends that will never go back to a system without using it.

This is another bad analogy but kind of valid, a cheap dac is simple an expensive dac will have more parts and components and software developed by the Dac designer to make the digital to digital conversion more accurate and sophisticated, typically the expensive dac sounds more refined, lowered noise floor and such this is what hqplayer does

I hope this helps

Edit, hqplayer has an internal basic player for local content which is very basic. It is also integrated in Roon so you can stream from roon to hqplayer directly qobuz or tidal or roon's library local content too. The pc holding hqplayer you connect via USB to the Dac or you send the audio via the network to a renderer pc, raspberry or what have you connected to the Dac 

In the mid 2000’s, I auditioned the Musical Fidelity Trivista 21 DAC. That was an audible wow. I kept that DAC for 15 years.

Traded it in for a Lumin D2 so I could play hi Rez streamed audio, and I kept it for two years. Demoed a Lumin T2 and within minutes it was “wow”. Shortest demo I’ve ever done, the T2 was so clearly superior to my D2 with LPS.

I still prefer vinyl but on hi Rez songs, the difference is closer.

Went from Bricasti M12 to the Nagra Tube DAC. I am done.

Stand out in my journey was AMR DP-777, wish I still had that to compare to the 10X in price Nagra DAC.