Hello Sipiric,
Very sorry to hear about your friend.
I see that your RME Babyface has two sets of independent analogue stereo outputs (a pair with XLR connectors, and a headphones output socket). Hence it would only be able to drive four speakers directly (as opposed to allowing independent routing to all five of your speakers, unless you also used additional ADAT DAC units with it?). From Deftech's website, it appears that the SuperCube sub-woofers don't have line outputs (to pass signal through to a pair of full-range speakers), so I'm not clear how you would plan to connect the sub-woofer? Do either of your pairs of speakers/amplifiers have line outputs to pass their signal on to a sub-woofer? Or do you have some kind of external mixer or other hardware device for that?
Presumably you'd like to set up full-range speakers as two independent stereo pairs of speakers, so that you could choose which ranks to route to each pair within Hauptwerk?