Hi, new here, been lurking for a while though.
To your question, I've shipped lots of stuff to Canada, and it can be a real pain for a shipper(customs stuff). I think thats why a lot of people don't like to do it. That said, I've been requested to ship USPS more often then not because it saves the buyers on customs brokerage fees. UPS, Fedex, etc. have to add somekind of fee for customs inspections.
Beyond that, Canada has import duties, which I think, run into the 10-20% range. And probably other fees or taxes. I would be sure and check all of that out before making a deal with someone here in the states, or you my end up with an unpleasant suprise, in the form of a huge import duty. 10% of a $1000 dollar amp is an extra $100 dollars. However, I think your currency is trading higher against ours, so you could make up some money there.
I hope this helps.