I would NOT recommend the Men's Warehouse. I think they are usually very high pressure. If you do shop there, get a suit and nothing else. The suits are a loss-leader (I think that's the right term). I don't think they actually make money on the suits because they are discounted. They make money by pressuring you to buy shirts, ties, casual Friday stuff, shoes, socks, cedar hanger for the suit, travel bag, braces, lint brush, etc...all of which is overpriced.
Also, I would definitely recommend shopping around. Don't let a place force you to buy something the same day you try it on. Don't let them start making marks for alteration until you are sure you want to buy the suit.