The Modi2uber is a decent DAC and will work with the Ember quite well, I'm using one with my Asgard2 for my lanai gaming/entertainment system. I haven't tried the new Magni2 so I can't comment on it but some have said that its a improvement on the original, also for me it would be going backwards from what I currently have, BH Crack, Asgard2, Lyr2, and Ember.
I started out using the line out of my Xonar DG sound card when I first got the Ember and it sounded pretty good, about the same as the original modi that I got a few weeks later. Original modi is okay if your sound card is really bad, most current motherboards have decent DAC chip sets so if you can't get a DAC at this time just get the Ember and save up for a decent DAC down the road.
Currently have a Bifrost uber and UD-301 with the Ember and these 2 DACs are pretty much end game for me as everything that I've heard that sounds better was way out of my price range, $1500+.