Nordstrom. Most of the sales reps are trained to know a good deal about suits and are extremely helpful in helping you find the right suit (YMMV base on location). They also usually have a place that can hem and do tailoring in most locations. Some even have a dry cleaning center located inside the store (also YMMV).

That said, they can at least recommend you something if nothing else. Those guys are required to wear suits all day too.