Shipping to Canada

Hello, I will need to ship several boxes of stuff from Brussels to Canada (Montreal). What is the best value way to do this? I can source and pack the boxes myself, and it doesn't matter to me how long it takes. I can also take the boxes to a depot in Brussels and pick up in Montreal. There will be some quite big boxes (containing musical instruments and equipment, mostly), maybe 5-6 in total. Thanks for any tips/recommendations. Also, how far in advance should I book shipping?