I'm not saying I don't like the MMB2, but I was listening to Daft Punk's 10th anniversary Random Access Memories and it felt like the bass was very loose, lacking definition. I took out the Aune X1S GT, and switching between the MMB2 and the X1S GT, it was obvious the bass was much better, with way more definition and without that soft lack of physicality (for lack of a much better way to put it).
There is also less "air", specially obvious in tracks where you can feel the studio, like Neil Young's On The Beach. There's this kind of halo around Neil's microphone that is almost totally missing on the MMB2, whereas the modest X1S GT can render it. I'm not saying the MMB2 is bad, just that that extra depth (not huge, but noticeable) comes at a cost, I guess.
EDIT: It would be great to know how the MMB2 compares in those regards (bass definition and airy presentation) with the Bifrost 2/64. I would upgrade to the Bifrost 2 or any other more expensive dac (within reason, 1000 euros is more than enough for me) that gave me that as well as the depth of the MMB2.
It's not hard to guess the 2/64 probably does them much better, but I don't recall the Bifrost 2 OG as specially textured in the bass. Anyway, if someone happens to have both and wants to add, it would be great. Thanks!