I am also a Canadian and i have boughten cars from the U.S. and brought them back accross the border. This is the way it works at the border. ..First you have to send the U.S. border a copy of the ownership with the serial number on it....then it takes 3 working days (Mon-Fri) for them to check and see if the car has been reported stolen before they let it clear customs. Then and only then are you allowed to bring the car across the border.
The last car I purchased was from a guy in Buffalo...after i paid him for the car he faxed me a ownership, I then faxed that ownership to the border, then 4 days later i phoned the border to ensure it cleared and was not reported as a stolen car...then i picked it up the following Monday morning as you can only bring the vehical across on a week day between 9am to 4pm.
THEMS THE RULES FOLKS
But if you do all the paperwork, it is not that complicated to bring the car into Canada...just do the paperwork first