I moved from and integrated to separates a while ago. Had already gotten a nice amp and was already enjoying it using the integrated as a pre before selling iit. In the interim between, I used my dac as the preamp to still very good effect. There were some qualities that were present that wasn’t delivered via the pre stage of the integrated, however at the sacrifice of overall sound stage. Nonetheless, I was still enjoying it, not exactly a dealbreaker by any means. But then, my preamp arrived…and man? If it didn’t completely transform my system. I thought at that moment “so this is what hi-end in my own room can sound like”. Strangely, things became more true to signal. Not less. More balanced, yet more real. It wasn’t stage this, clarity that…it was everything combined, a major change toward hearing what the artist/engineers were intending. Really, the first time I was experiencing goosebumps on the regular.
To me it really seems it boils down to that output stage, output gain and synergy with your amp/speakers. I’m still wondering, however, what a serious dac with a profoundly well built analog output stage might still do on its own? Still wonder about that more direct path when applied well. But it would need to be configured with the right gain (or gain flexibility) along with the latest discrete design topology. Tech is improving rapidly, and it’s very regularly applied to audio gear. Not doubting that it isn’t already achievable, just not (yet) as available in the more affordable range.