Paul,
There is a large contingenet of people out there who think adding a preamp adds to the quality of the signal headed to the speakers. these are mostly the people selling preamps. Add to that those who have bought a pre-amp and want to defend their position.
Certainly adding a pre-amp will likely change the sound. Different doesn't mean better.
I"m a purist, similar to what you've described. the best the music can get is what is recorded on the source medium. as you process and amplify it, you can't add anything, only subtract from the perfection that exists at the beginning. The less you touch the signal, the better off you are.
So I think you are exactly right to use your DAC to feed your amp. I do that with my Chord DAVE.
Thanks for this thread, it did create the funniest statement I've seen on audiogon for a while. "DACs reduce vollume by dropping bits." Great plan: this guy is listening at low levels so he doesn't need all the music. we will just throw some of it away. Great example of how people don't understand digital.
Jerry