Fellow Canuck here too

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We have always purchased our tickets direct from DC. The price via DC direct has always been cheaper than vs. CAA or through Expedia....for our August dates, its a substantial difference! ($259 pp via DC directly, and $386.47 through Expedia.ca).
I am not sure if the Expedia price includes tax, but even after tax and a 10% exchange (since our CDN $ is sitting at about 90 cents US right now), that still would put DC at about $303 vs. the $386.