Haven't you heard? A stereo 15W amp is all you need if you are an arranger player?
(Still waiting for that 'tongue-in-cheek' emoticon!)
I can't comment about the K series specifically, but I've played in many bands and venues with QSC amps, and they've always been reliable no nonsense workhorses.
Funny story... I went out on the road for a few days, and in the meantime, my wife (now sadly, departed) decided to hook up my little PA to listen to some music. Knowing next to nothing about audio, she accidentally connected the outputs of a little QSC 100WX2 amp to the inputs
and ran it for HOURS before I got back home... You could cook an egg on it by the time I shut it off. Powered it back up after it cooled down, and it still worked like a champ!
Great stuff...