I'll put my 2 cents especially that the Canadian Dollar is actually worth something now.
The sigma 70-200 is a great lens, but it is not on par with the Canon 70-200 IS. I have done some simple tests with both lenses and there is a noticeable difference in focus speed between the two. Now don't get me wrong here, the Sigma is a great lens, just stating the facts. Chili has the non IS version of the Canon and I have heard they are not as quick to focus as the IS version, but I have never tested this for my self. Now to clear things up, this as far as I can tell only applies to situations where you are shooting in low light, so in other words it doesn’t make a difference when shooting outdoors in the daylight.
As for a something a bit wider, the sigma 24-70 2.8 MACRO is a great lens. Probably one of the better lenses I have ever used. I tried a Canon version and I actually prefer the Sigma over it. The one thing I don't like about the Sigma lineup is the zoom ring works in the opposite direction of the Canon, so that can be a bit confusing.
Good luck.