Flat and incline bench press build the shoulders and chest, but I wouldn't really say it, "widens" the frame. It gives an illusion of it IF the chest muscles can be seen, and that's only if you're bodybuilding and only if you've been doing it intelligently for years.
Decline bench press really hits the lower chest. It's the ONLY excercise I've ever heard anyone complaining of, "putting on too much mass." A lot of bodybuilders say that doing this builds the lower chest so much it gives them saggy boobs. The fact is that decline movements, flyes, dips, and bench press, are the most effective way of hitting the pectoralis major, hitting a much larger percentage of its fibers than any other exercise.
The bench press is a great exercise, but don't forget the legs, and remember for every push, you need to do a pull, SO DON'T FORGET THINGS LIKE PULLUPS AND ROWS EITHER.
I bench 200, close to twice my BW, I win at local and state powerlifting comps w/ the WPU and so I figure I'm a decent authority on the subject, hehe.
Honestly for widening the frame you need to do things like side laterals, upright rows, and overhead movements to hit up the shoulders. Deadlifts wouldn't hurt either. To get WIDE, you need to work on pullups, any kind of rowing or pulling motion. Gymnists are the widest mofuggs on the planet and it's from doing pullups and crucifix thingies all day.
