It is really quite nice as well. As mentioned I have been using it in my office for quite awhile. I really had no motivation to replace it as I have been really happy with it driving any of the closed back cans that I use at work. This has included the Aeon, PM-3, HP50 and AKG 553. It has a very smooth presentation quite in line with it's AKM DAC chip. It has plenty of power for anything that I have plugged into it. The BL just adds a bit of energy to the recipe, and it is a new toy. If I had not found it new for around $360, I would not have bought it. But that is just me, and the fact that I was that satisfied with the M9xx. Now, I only spent a very brief amount of time comparing the two units. I had brought it home because another member wanted to know how the HE-560 sounds with it. BTW, I like the 560 very well with the M9xx. Its signature is very nice with that headphone that, to me, can sound a bit thin. I have seen the M9xx for sale in the $300 to $350 range. At that price versus the BL at $550, I would grab an M9xx. With a deal like I got, then it becomes basically a toss up. The choice would then be down to an individual's signature preferences.
EDIT:
One thing that may be a consideration. Both DACs will do DSD 256. The BL natively, the M9xx took some playing around in Foobar to get it to do that. The BL will play DSD512 natively as well, for whatever that is worth.