thanks Alan, its rehearsal and gigs. Maybe I found a solution: if i reduce the volume in the amp section (i.e. the amp volume itself) then i get a little more control of the powered output. I usually leave the volume of an individual amp at 0 dB; maybe that's the "mistake".
So far i dont think that reducing the amp volume (e.g. - 7.0 dB) has a dramatic effect on the sound of the respective amp. What do u think of this solution ? (Of course I will have to up the gain on the mixing desk, but that's not an issue.)