I haven't heard the Mjolnir, but I have the Stagedac (Daccord predecessor) and Classic and the original Bifrost. FWIW here is a chain of impressions.
In a comparison review I did some 3 years ago I found the Stagedac more balanced, transparent and 'right' than either the Eastern Electric MiniMax (worst) or Bifrost (very good). Amps used were Meier Concerto, Schiit Lyr with the stock GE option and (briefly) the Stax Lambda Pro with stock energizer. Other hps used were Audez'e LCD2r1 and Beyerdynamic T1. I understand Daccord is a better Stagedac, and as I found it (slightly) better than Bifrost...
Recently I bought the LCD3F and was amazed how much better it matches the Classic than does the LCD2r1. Particularly noticeable is the excellent layering and very good sound-stage. This was true even with (very briefly) a humble iPod Classic 120 as the (analog!) source.
Worth noting, I usually pair the Classic with the BMC Puredac. This dac is a considerable improvement on even the Stagedac in terms of fine, low-level detail which continues right on into the bass. These are important attributes for any Audez'e, which repays every bit of quality it gets from the upstream chain in the bass and lower mids. Some of the reported attributes of the Gungnir do suggest it might be right up there with these important aspects of the puredac. Provided the G/M combo matches well with fazors, I imagine it could be hard to beat.
OTOH, the Stagedac and Classic do everything well and nothing or very little wrong.
Note: The Classic usually plays "2nd fiddle" to my main amp, which is tube-based and cost twice as much. I find the Classic compares extremely well.