How do I make sure this watch is Genuine?

[space-time]

Let's say that I decided on a particular model (I am still not sure though)

Directly from Tissot, $425

http://shop.tissot.ch/mm5/merchant.mvc?Screen=PROD&Store_Code=&Product_Code=T17151632&Category_Code=m_all

or same model from JomaShop for $252

http://www.jomashop.com/tissot-t17151632.html

How do I make sure I get a real Tissot watch and not a Chinese $10 replica?

Also, JomaShop sells one that is NOT listed on Tissot's site, do you think it is real of fake?

http://www.jomashop.com/tissot-t17-1-526-52.html (EDIT: correct link)