I got both my Tamrons online from Ted's Cameras, but they also have a store in Sydney and they advertise that they will price match.
I decided to go this way for the peace of mind of the local Tamron manufacturers warranty. I have a rule of thumb that if the item has a motor and a PCB I buy from a local authorised dealer.
I usually start my buying search with Static Ice to get a ball park figure of what prices are on offer. http://www.staticice.com.au/cgi-bin/...mm+f2.8&spos=3