I have been running a 160 for years. I only drive the car in the non winter months. When it was dyno tuned (After I did a heads and cam change) the tuner set the fans to come on at 180.
A t-stat change by itself will NOT do all that much, it will just take longer before it gets to the same temps as it did before.
You need to have some type of fan control to actually get the car to run cooler. Do a search, there is a vendor on the forum that sells a kit, or you can make manual switch.
I would go with a 180 if you drive it in the winter - but it also depends on what mods you made and what the winter is like where you live.
Vararam / LS6 / PRC Stg1 / TSP-228R
XSPower / Corsa
429hp : 395tq