Yep, I'm pretty much in line with Scott Yee on this question. One thing I like to do is to aim the PA speakers such that their projection paths cross about 15 feet in front of the stage area. I also output the left channel of my keyboard through my Peavey KB300 and the right channel goes out via the PA system - gives a nice split and really throws the drum fills, etc. about quite well. Of course, there are all kinds of permutations for this sort of thing. Many times it'll depend on the room you're in and the characteristics of that room.
Happy playing!
Big Red