If you think your preamp is adding quality to the presentation, where is it getting it? I like to look at the signal path as 100% as digitally stored on the medium. Every time you touch it to DAC it, to preamp it, to amplifty it, you try not to degrade it.
I'm a minimalist when it comes to signal path. Great tube amp designers agree. I use my DAC is my preamp (since I listen only to digital signals).
Keep it as simple as possible.
DAC is Chord Dave.
Jerry