It all depends on the gear. If manufactured in Canada then typically yes its cheaper up here. If made in the US then you're better off buying it at home because the current exchange rate is hovering around 50 cents on the dollar so something that costs $1000 US will cost you $1500 Cdn. If you are looking to buy Classe, Bryston, Paradigm, Energy, Blue Circle, Coincident and a host of other nicely made "Canadian" gear then the trip may very well be worth your while. You will pay provincial and federal sales taxes (depending on the province, Alberta just the federal tax) and apparently there are forms you can obtain to get reimbursement. I believe that the federal tax (GST) can be reimbursed on the spot if when returning to the US you stop in at the duty free shop before entering into the US. The provincial tax will be reimbursed by the Province when you provide them the proper paperwork.
Decide on what you will be looking for and look-up the website for the manufacturer to determine the closest
dealer(s) before you start your trip. Call ahead to determine if the local dealer knows anything about the tax issue....Come on up and spend your money eh!