Just returned from a week in Montreal and QC filled with great eating experiences; you are fortunate to have so many good places in both cities.
The best meal was definitely at Garde Manger, one block from our hotel. I took the NY Times reviewer's advice and got the steak frites, and they were easily the best I've ever had. We tried to go back another night, but they had a sign on the door saying they were filming some kind of TV show.
We also loved Stash Cafe just down the street. Trust me, I've eaten all over the US and have found only a few good Polish restaurants that rise above the level of humble lunch counters. This place, with its church pew seats and many posters of Polish artists, looks as great as the food tastes. The sampler platter of bigos, pierogi and other foods was wonderful. Plus the service was good, even on a busy night.
Our first night we ate at DNA which was good, but which we both felt was trying a little too hard. Awesome lobster risotto, though. And of course we squeezed in an obligatory visit to Schwartz's, just barely beating the massive crowds.
Speaking of sandwiches, another highlight were the incredible banh mi at Cao Thang on St. Laurent. I ordered the #4 pork meatballs, spicy, and was in absolute heaven. The sandwiches at Olive & Gourmando were impressive, too, especially the goat cheese and grilled onion with the house-made ketchup. I would eat *anything* with that ketchup.
In Quebec City we had a pretty good seafood meal at Marie-Clarisse, though unfortunately they seemed to run out of things (like sea bass) at a fairly early hour. We also enjoyed the game dishes at Aux Anciens Canadiens, though the portions are so massive that it's a shame they have a policy against taking away leftovers. The desserts in particular were enormous.
We also ate pretty well at Le Cochon Dingue and Cafe Le St. Malo even though both places were completely overrun with tourists and I'm sure the food/service were not at the top of their game.
Anyway, I'm definitely going back soon!