Turboace,
Both seem to be good choices for both home/small stage gigs. But beware about the sound behavior in the 300 seat school environment, because depending on the acoustics of the room (reverberations, etc) / number of people present, etc, even with a very powerful amp, without proper equalizing, the sound, tend to be dull and messy and not perceivable at all.
But that doesn't mean that the KC150 and KC350 are not good choices...
Hove you seen SA-300 ? Portable mini PA ? it is awesome for keyboards, guitars, voice, drums...and is very portable.
Make Music and be Happy !!
PauloF