I really like Michel brisson on Laurier Avenue (michelbrisson.com)
SSense (ssense.com) in the old Montreal of course (They have a sale at the moment, if you see something you like on their website you can have them transfer the item at the boutique to try it on in person) Takes 1-2 days usually.
Holt renfrew in the basement is nice too
Boutique Duo on prince arthur street
Those are my favorites...