OK.... here's my two cents.... or fraction thereof... ;-)
the stock t-stat is a 195, if I am not mistaken. Dropping in a 170 degree t-stat is just going to open the engine to coolant flow sooner. As mentioned, if you have a coolant system problem.... for example, air in the system (unlikely if you drive it often as the system self purges - might not be perfect, but it will happen) or damage radiator, the car will still run hotter at it's max. However, if everything else is fine... the car will run with a more "constant" temperature if the t-stat temp is lower.
The Viper has a 195 degree t-stat. When I had mine in the car in Florida, 95 degree heat, no breeze in the summer, high humidity, etc. when driving around town, averaging 50 MPH, stopping from time to time at a light, for example, the car runs at about 190 to 210 degrees. This is normal. What happens is that the temp will move up and down as you cycle through the t-stat opening and closing. The reason is if the water is not moving through the engine it will cool down more and more as it travels through the radiator. When the t-stat opens... cooler water comes in, temp drops 20 degrees. If I was on the highway at 65 (that's my story and I'm sticking to it) the car would would cycle up and down as well but the swing was lower. It was basically about half the move that we would see in the city.
With the 170 t-stat in the car the car stills cycles in the in-town traffic but now because of air flow over the radiator. However, it cycles from about 180 degrees to just under the 210 degree range. On the highway, with constant airflow through the radiator, the car will hold in the 180 degree range steady. It will not hit 190 degrees at all. I just drove Miami to Orlando and back this weekend (500 mile round trip) and that's how it ran.
Bottom line, the lower t-stat will keep the engine running cooler overall because the coolant flows sooner. So if there is going to be a 30 to 40 degree swing (normal) in the temp range when driving, it will be from 180 (more or less) to 210 as opposed to 195 to 225. If you are on the track, heavy load, the temp will still max out higher, regardless of the t-stat, but under normal driving... it will run cooler.