Top notch integrated vs DAC direct into stereo amp

DAC into integrated, any day of the year. I have not played at your level. But been trying to eliminate preamps forever it seems like, and I can’t. At your level, you are not short of funds, why would you, it doesn’t even make sense, given how much preamps can bring to the table. And at that price point you will get an integrated with a preamp stage that will be world class.

I am not going to make a blind recommendation on gear I do not know. As I said, either option may be superior based on real world systems. 

In my experience a Bartok or other great DAC will sound better into a similar quality integrated amp such as the new Agostino ‘budget’ integrated amp. Same for Dartzeel. Only ones I’ve had in house. I just don’t like direct but wish I did. To sum up my opinion is that the chosen DAC used with a Dag or other high end integrated amp will sound better than even going direct to an S250 which I’ve owned. FWIW

Totaldac has something called the D1-Driver for people who want to go DAC direct, this might me an option : http://www.totaldac.com/D1-driver-en.htm

Audionet describes their Humboldt as Stern + Heisenberg.
That with a great DAC would be killer.  So would the Stern + Heisenbergs.

The Humboldt power is listed as : 
Output Power 2 x 320 W into 8, 2 x 460 W into 4.

The Heisenbergs would be:
Output power:530 W into 8 Ω
1,050 W into 4 Ω
2,100 W into 2 Ω

So the difference in a companies Integrated vs it similar separates is often the power rating, which you may or probably may not need based on your speakers and room.  And you save a pair of (expensive?) interconnects with the integrated, and save considerable space.  Those are the main reasons to consider integrated vs separates, to me.