I can only assume there is still a market out there for the non-USB, no internal amp DAC.... In fact, it would be me! I don't have many sources that I use USB from, and since I own a few amplifiers already I don't really look for my DAC to come jam packed with one... In my case I'd like all the $$ to be going into the DAC side of things.
That said, there is something to be said for the amount of features these things come loaded with now... and the fact that the headphone amp isn't total crap is impressive, right?
Maybe I should be checking out the D18...
I agree with you that once you already have a system and are only looking to upgrade certain parts of it, devoted components would generate more of a drive to purchase, but I think for newcomers or someone who just wants to get something and be done and still satisfied with the system to a certain extend, integrated DAC/AMP definitely has more attraction.
As for D18, so far it seems that only Project86 owns it, maybe he should do a loan program/test listen too. I have been holding off simply because it's Christmas and I have so many other things to spend my money on, but maybe in the next few days I won't be able to stand the itch and will simply buy it.