"I want to perform live with a KM184 or AKG414 mic on my acoustic and play through a portable but decent preamp."
Check out this link where Bob Brozman discusses what he uses for house sound, and why.
It might have some info that will help you. http://www.bobbrozman.com/soundhints.html
He's speaking about National resonator guitars but I believe his advice can be applied to acoustic guitars in general.