i asked the question once. with out having a performance chip in the car there is not benefit to having any other thermostat other then the stock one. A I have heard that will can also cause unnecessary engine ware.
Without having a chip that tunes your car to run cooler, there is little benefit from a lower temp thermostat. Although with you in Arizona, if your car runs on the warm side of normal anyways, I would throw in a 180 degree thermostat.
About the comment about a lower temperature thermostat...... I have heard that prolonged use of a low temperature thermostat could accelerate wear on the engine. (kinda like how beating on the engine when it hasn't warmed up isn't a very good idea.)
I had a 160 degree thermostat in my 1991 Z24 for about 20,000 miles and a little over a year when it was totaled. When I disassembled the engine, I didn't see any abnormal wear on any of the bearings or the cylinder walls. Granted, I only had it in for 20,000 of the 90,000 miles that are on that engine, but that is my personal experience.