on a car where everything is operating correctly, a 160* thermostat will open and allow coolant to flow through the motor before a 180*. but if all that is happening is that the coolant is flowing through the motor, and you don't have your fans working with the thermostat, then no, i don't think you will see much difference. as already stated, if you don't program your fans to come on earlier in the temperature cycle, then all you are doing is allowing the coolant to flow through the motor.

think of it like this: a 160* thermostat will open at 160*, which is earlier than the 180* thermostat, which opens at 180*. if your fans are in sync with the thermostat, then you will notice the car will run at a 20* lower temp than normal (180-160==20).