I've looked into purchasing a new car in the US as well (savings of approx $14,000), but have been told by an accountant who specializes in Canadian/US inpat/expat work that if you are a Canadian resident and you buy a car in the US, and then import it legally into Canada, you are not able to ever resell the car in Canada. He swears that the only people who are allowed to resell US cars in Canada are registered dealers, or former US residents who have moved to Canada.
Have you looked into what happens when you decide you are done with the car you brought in from the States? I know that when I have had my current car appraised as a trade-in, I am always asked if it is a US car.