Ive seen reviews that call the BF2 a mini yggy with very comparable sound... Especially single ended... More similar to the yggy than to the gugnir in sound.
Torq says that if a Dave fed by mscaler is 100,, the yggy is a 98 and the BF2 is a 95/96, if I remember correctly. He says the BF1 is about a 90 on the same scale.
Both make his top 10 list, even compared to 5 figure dacs... Pretty high praise.
Another comparison I've seen also describes them as very similar with the differences being subtle... The example used being the BF2 is like a single high definition screen and the yggy being multiple smaller panels assembled together - making it slightly easier to identify the individual 'space' of each instrument, whereas the BF2 provides a little more blended sound - but overall tone and presentation almost the same.