Deserres has, IMHO, the best canvasses in the city. They used to carry gallery wrap canvasses in all sizes with really thick and sturdy stretcher bars (be still my heart) but now the manufacturer only puts that wood on the really big canvasses (say, 30" x 40" and up). The manager sympathized with me and blamed the times. But I paint big and love those well-made gallery wrapped beauties.
They also have a great selection of unusual printed or hemp papers by the sheet for collage or wrapping, or just drooling over.
The Eglinton/Yonge branch seems to usually have a spot to park in front, whereas the one on Spadina involves carrying my 60" x 40" canvas through the side streets to where I've parked. They will deliver (for a fee) so it might be best to order a bunch at a time and sit back like royalty while someone else carries these wind catchers. Only trouble with that is you don't get to pick your own canvas and I've had canvasses delivered with corners damaged/dirty.
They have a customer appreciation program and good sales. I wish they still sold oil sticks, but those I get at Above Ground. Otherwise I feel good shopping here.