I have the 2 audiocard RME : Babyface + Fireface 400.

I have 2 keyboards + 2 Monitoring systems : Dynaudio (2 speakers BM12+ Sub9) and K&H O110 (no sub).
At the moment the Babyface is linked to my Macbook and the KH and Fireface is linked to my iMac and the Dynaudio.

What would be the best way to link all that : let both cards work each on its way like now or link the 2 RME cards allowing all kinds of combination.

I am interested in that second solution and would need some help to realize the linking....

Thanks for your help;