I agree with Budrew right down the line. I've owned the Audio Note 3.1x Balanced, and recently upgraded to the 4.1x Balanced Signature. "Natural, smooth and engaging" is a common thread that runs through all the descriptions I've read of the current non-oversampling AN DACs, and I've heard it even in their entry-level DAC Zero - the one that convinced me to buy into the AN lineup.
I'd add to that list of qualities a sense of "you are there" realism, and bass that breathes like it does in real life. There seems to be much less of an electronic flavour to the sound compared to other DACs. Compared to either of the AN DACs, the SimAudio Nova in my living room system sounds sterile, bleached and artificial.