Hey mate I've seen you ask a few questions and while this is kind of late I'll chime in for a second. If you still haven't bought one you can pop into bartletts hifi to demo the m1/m-dac. I absolutely hated the MF DAC. It's huge and sounds waaaaaaay too forward IMO. I listened to 2 tracks and then stopped auditioning it, it was that bad to my ears.
True that the mdac supply is kind of a joke and this is a good reason to think of smthg else. The Rega DAC is £100 more and just owns the M1 IMO. Some say it's warmer so if you like that then there you go.
You asked about USB somewhere and from what I tested it is better than the optical inputs. Is that to do with poor implementation in my macbook pro? I don't know but it did sound better and it is also a lot more convenient.
You really have to demo because I don't think the m-dac is lacking in dynamics so our tastes seem to be way different.