best card for Canon ti4

I just got a Canon Ti4 camera.  Is a class 4 card adequate or do I need a hihger class card?

Recommended cards by SanDisk are the Extreme line, class 10. Which gives a higher transfer speed than the class 4 cards.
Best thing to do I think would be to contact Canon also to see if they have a minimum speedclass recommendation for cards to use with these cards.