combining amplifiers for live sound

I know this is not a recording question but would guess some of you might know how to do this.
I have a berry pmh3000 powered mixer.
When playing a large room or outdoors the berry just is not loud enough.

Is there a way to combine the powered mixer with another amp???

The berry has speakon cables and all of our other amps have 1/4" plugs.
BTW, I like the sound quality of the pmh3000 and the mics that came with it work very well also.

How do you run the unit now? Do you run both mains & monitor off it? If so, one suggestion would be to put it in bridge mode which will give you 800 Watts for your mains and get a separate amp for your monitors.

You can “bridge” mixers but you can’t really bridge power amps.