Hi rperes,
the Micstasy has no D/A. Otherwise it's one of the best Preamps on the market, sounds just excellent. If you need more D/A than the HDSPe has (one Stereo), you could either take an ADI-8QS(M) if you want to connect by MADI, or take a cheaper ADI-8DS and connect it by ADAT to the Micstasy. You can set the Micstasy to convert 8 channels from MADI to ADAT (great feature!), this way Nuendo playback will be sent to the analog outputs of the 8DS.
Set up: PC(HDSPe MADI) <---------[Duplex MADI cable]----->Micstasy---[ADAT cable]--->ADI-8DS.
Max

About the outstanding quality of the Micstasy: Here is a video from the swedish classic label BIS, recording with the Micstasy: http://www.youtube.com/watch?v=ERfxPWCW4yM

best regards
Knut

it's quite common to use two recording systems (even if you only needed one). even though it would be enough to copy the files after the recording, you don't want to let the musicians wait if one of your DAWs get's swine flu.
a logical way to connect the two madifaces to three micstasies would be:

madiface 1 optical ---> micstasy 1-----> micstasy 2 -----> micstasy 3----> madiface 1 optical input and madiface 2 coaxial input (since RME MADI devices always carry the MADI signal on both optical and coaxial outputs).

in the movie, they seem to remote control the three micstasies from DAW2 (lower Madiface). that's why they plug the optical output from madiface 2 to the first micstasy.