I think I need more power.
I previously played in a group which had 12 or 13 singers (depending on the song), a drummer, keyboards, two guitarists, a sax, trumpet, and trombone.
I refused to run through the PA because our director (who was a choral director, not a sound man) refused to run monitors or a hotspot, and I always had complaints from the audience that they couldn't hear the guitarists at all (who were running through the PA), but could hear me perfectly, maybe even too softly.
I was constantly on the verge of clipping with my GK 700rb and 115 cab. Even when I ran through the PA, I couldn't hear myself. I wouldn't really need two 810s, but I would've really enjoyed having an extra 100W of head room and 410.
Just goes to show that some sound men (or women) are out of their element and do not understand how to operate a backing band. Many times I had audience members suggest that our band (who was more talented and driven than a majority the singers) should just quit and have the director use a CD because he wasn't utilizing our talents enough.
In conclusion, different strokes for different folks. Use what you feel appropriate.