Yes that is an excellent way to set up your PA! I am running:
Monster Pro 3500
A&H Mix Wizard
Sonic BBE 882i
Driverack PA+
QSC KW153's (mains)
QSC KW181's (subs)
QSC HPR153i's (monitors)
I am thinking about getting another PA+ or a PX for the monitors for the same reason you are...