Thanks for your quick answer.
Oh yes, using an analog stage cable back from stage to FOH is the simpliest way, I already had known it, therefore I did'nt mentioned it. However, a major objective for switching to digital mixing world for me was the possibility to save the big "snake" or as a minimum to need only a thin CAT5 cable. Okay for a short "migration" time I can use a my small 8 channel multicore I have in stock, unfortunatelly it is only 20m long.
The alternative of audio over ethernet sounds interesting, if it can run at the same cable as used between the PC and the RM32 via an Ethernet router? As I understand is the "One CAT5 cable can handle 4 XLR signals" only a cable adaption and not an electronic solution, isn't it?
As I understood is the standard solution with an iPAD (e.g., via wireless router) only provided to control, e.g., monitor / sub mixes etc., but can not be used for transfering beside the control commands the result of the mix to a headphone for instance connected to the iPAD directly, isn't it?