I have heard that the stock one is a 180 deg. unit and opens in stages according to temp. (justifying the approximate $100 cost). I would look into this and make sure before you replace a $100 engineered part for a $16 one-size-fits-all part. I considered replaceing my stock stat until someone told me this. But then again I have never verified this information. Please post if you find out for sure what the stock one is.
The stock unit is 180 I'm looking at it right now. Put in a 160 thermostat the fans will only let you run so cool. I have the 170 and I should have gone 160. Or you could just drill out the factory that will work.
Correct me if I'm wrong, but I also read that if you go with a 160 deg, you have to set up the fans to turn on early. Otherwise the computer will go crazy. You can do that with a tuner like Predator or a chip.
When you change t-stats you have to set the fans to turn on early or you car will continue to run at the temp it does now. Not really a must mod in my opinin.