If you know a person from the US whom you can trust enough to get a Falcon Northwest rig built and shipped to their address - they're pretty rocking.
www.falcon-nw.com I don't think they ship to Canada, but I could be wrong. As far as I remember, they don't.
http://pc.ncix.com/ncixpc/ also has some pretty good deals here and there. If anything, it'll give you an idea of what kind of computer you want, along with a ballpark figure as what you're going to spend.