I was going to reccomend the Grado sr125's for your pricerance, but those would be too cumbersome for excerising and too loud for work. so id have to go with the Etymolic research phones. They are small earbuds which go in the ear canal and are supposed to be really comfortable and block out a good percentance of sound because of the way they seal into your ear. I think the cheapest ones run about 120 bucks.

Haoleb's Audio/DIY Website