Andreas –
The only consoles in the entry price level that I am aware of that are phase coherent THROUGH THE MIX BUSSES are the x32/m32 series from Music Group. I have no info on the just announced/released models from Allen & Heath, Yamaha, Avid, Roland, Digico, etc., but on most digital consoles, paralleling a signal through different “length” pathways (ie., #1 straight to LR, #2 through a mixbuss then to LR) introduces latency which causes the “phasing” effect on the signal, which is most noticeable in the higher frequencies, such as vocals…) I learned this in 2006 on an LS9.
Even the x32/m32 will suffer this problem if an effect or signal processor such as EQ is INSERTED on one of the paths of a split signal.
-Tim Tyler