UPS always does that, no matter how big or small your imported package is. They charge canadian/ontario pst and gst taxes to any package that comes into Canada (that's 15% added to the total cost) plus their inflated brokerage fee, which would add around $200 extra to the order.
No matter how you get that system into Canada, be it driving it across the border yourself, having delivered by the post office, or delivered by UPS you will always owe the GST (federal) and PST (provincial) tax.
There are no "duties" on computer parts coming into Canada (at least none that I have paid).
Canada Post (at least here in BC) charges a $5.00 "handling fee". That is the only extra charge.
If your supplier insists on UPS see about upgrading from ground service to air. At a certain level of air service UPS charges less in fees and at another level there are no fees at all for customs clearance. All you would end up owing is the PST/GST. Your best bet is to call UPS and ask which levels of service incur which charges. It may turn out to be cheaper to send your computer UPS 3-day air and bypass some of the fees.
Just some friendly advice... :-)
