Think about it. People upload files to you, but they also download them. If you download from someone with 56K, then you may not get all of that bandwidth. What if that person was also surfing the web? That takes bandwidth too. If you were the only one downloading, and no one else was, then you might get it all. Besides as you are using dial-up yourself you should know that you almost never get a connection above 4.5. (5.6 is actually above the maximum limit set for dial-up by the government, which is 5.3) If you were doing anything that takes bandwidth, then you will also have you bandwidth split. (checking email, surfing, ect.)

If you want to get better speed, get better access. Even with broadband, you still may find yourself downloading from a slow connection.