Ever-ready to play devil's advocate, I will take a different tack.
Your McIntosh amp is pretty "warm" by itself and I imagine that you don't really need to double up on the tube output. If you can find an EMM CDSD/DAC6 (or DCC2) combo available to try in your system, you may find that you like it. I find that its accuracy creates its own "warmth". The lack of harshness creates a fluidity and sense of "rightness" which by itself is just plain natural. It is seductive (full disclosure: I have the combo and cannot imagine letting go). The DAC6 gives multi-channel DAC output which will work fine with your integrated. If you went for the DCC2 instead, you would have a pre-amp function if you ever decided to go for separate amplification.
While I do not know the "sounds" of the Audio Aero and Audiomecca above, I know a few people who have used at least one of the two and many also liked the Electrocompaniet EMC-1 [though whichever one was owned was obviously worlds better than the others :^)]
In any case, the most important factor will likely be how the chosen DAC/McIntosh/B&W combo works together so I cannot but recommend an in-system test.