I have a 700 and sure it is an upgrade from the Bluesound You can use it just as a streamer but would not make much sense by paying a bunch of extra dollars for the Dac system.
You may want to look at an Aurender streamer as an upgrade to the BS
I'm going to assume the MM Ultra is suggested because my bottleneck is the dac in my Anthem str? That's a $600 to 10x difference in price. I like to buy something once and pay once instead of upgrading in increments. I may have to ultimately look to change the Anthem and/or dac to make this work.
Does anyone have an opinion on the aforementioned Innuous Zenith mk3? It's a streamer that seems to have gotten a nice upgrade to the sound. I was originally thinking if I were to get that, then a few more dollars could get me into the CA 600 or 700. Then I would always have the option of using the days included.
I'm probably still waiting for an all in one to get rid if so many cables and boxes, but I got antsy when I saw some used MK3s and DMS for sale. The latter would go nicely with my Paradigm Persona speakers.