I took a 4 piece band out last weekend on two occasions, and had to amplify another singer and a sax player. Since my mixer is only 4 channels, and I have it neatly filled with all my requirements, I decided to give the Korg as shot as a sub mixer.

I put the sax mic, and the other singer's mic directly into the PA80 and used the vocal board's EQ and effects. - BEAUTIFUL !
My mic went direct to the Digitech, and since it was a large party, I had plenty of "oomph" to listen too, and didn't miss the on board monitor. ( I actually shut off the speakers, because I didn't want sax in my face all night - sorry Boo )
Yup - you heard me right. I shut off the speakers. (I drarely do this, but the volume was such that the on board system was a non factor anyway, and I DID miss the closeness of the sound)

The submix solution was a winner, and in the future, I will have 2 extra mic inputs when needed. Of course, the other singer could not use the harmony, because it would trigger the switch for the sax as well, but hey - nothing's a perfect solution.

All I wanted to say was this:
The PA80 has a great dual mic preamp built in, and it works as it should, and sounds as good (or better) than any other mic input out there. I was pleasantly surprised ..... but only a little. I really EXPECTED it to be fine. Nice when it all works out.

Happy Fathers day to us !