Here's a description of the GWS EPS 280 motor power system. Just follow the links.
My understanding is that the 'standard' EPS comes with a 280 motor and the 'deluxe' EPS comes with a 380 motor.
The IPS power system (as opposed to the larger EPS) from GWS, which we commonly know as the '180 size' DX-A Lite Stik motor/gearbox will only fly a plane of upto seven ounces. In other words, you need a 'EPS' 280 power system for a 16 oz. airplane.
Don't know if anyone carries it yet, but price should be in the twenty dollar range.
Hope this helps.