i never heard of a thermostat & fan switch making the car warm up quicker!!! the thermostat only opens when it reaches a certain temp. it does nothing to add heat to the heating system. same w/ the fan switch.
are you having problems w/ overheating? if not, why go w/ a lower temp thermostat?
from reading other posts in a jeep forum before, the guy that works as an engine test guy around the motor city area said that when the engine is running cooler, not up to "design operating temp," the piston rings wore a lot quicker than normal. he never did post what the testing temp that the engine was testing at...
imho, i would say yes to a lower temp thermostat if you're modifying the sh*t out of your engine, i.e. supercharging or turbo, since you're adding a lot more heat due to the higher output.
good luck.