BuyDig.com offers the TomTom XXL 540M 5" Portable GPS Navigation System
, model no. 1EP0.052.09, for $169. (Add it to your cart to see this price.) With free shipping, that's the lowest total price we could find by $16. This GPS features a 5" touchscreen LCD, lifetime map updates, maps of the US, Canada, and Mexico, advanced lane guidance, EasyPort mount, and more.
Update: Amazon.com has it for $168.84 with free shipping.