what kind of headphones do you have?
bose makes in-ear headphones, and on-head headphones
the on-head type has ones that go on the ear (supraaural), and those that go around the ear (circumaural)
etc etc
the point being, if you want to hear your source better, its better to address the problem with solution like (active) noise-cancellation, or (passive) sound-isolation. [latter is my preferred choice]
simply making your headphones louder, is not really good for your listening health.
i think bose uses NC. if thats not effective for you, try sound isolation products.
further, amplifiers can, but dont necessarily raise the absolutely loudness level of your headphones. it just makes the sound better / less distorted at those louder volumes.