You ordered a 2000$ computer from the US? Even if things are cheaper there, it's usually not worth it because of duty fees and taxes...
Here are a few tips:
1. Don't order from the US (unless you go pick it up yourself there). Try to buy online from another province, this way you don't have to pay provincial taxes. ( I live in QC, so it saves me 7-8%, which is better than nothing)
2. If you do buy something expensive, buy it through borderfree.com. This way you know exactly what you'll be paying. Also, NEVER have anything shipped with UPS. They are the only company that charge brokerage fees ON TOP of the duty fees and taxes. (not to mention they basically break everything they touch...)
3. You could try marking the item's value to less than 40$, but this is hard to do with retailers. Also, the problem with doing this is that if they break or lose your package, than it's insured for the amount you declared, so you're screwed.
4. Marking items as gifts used to work, but not anymore. I guess they noticed people were abusing this, so they don't care anymore, they charge you anyways. And it's even worse if you don't put any value because they'll open it and evaluate it themselves. ( I once paid 40$ in taxes for an 80mm computer fan)
Sorry to tell you this, but you'll probably end up paying more than you would've if you had bought your computer in Canada.