Yo,
If you really want to juice your connection, go to
Speedguide.net. I did the tweaks that this site recommended and using their analyzer, really sped up my connection. It will really help your connection.
These "accelerators" usually go one of two routes:
1: tweak your connection -- that's what speedguide.net does for FREE
2: pre-fetches pages -- basically it follows most of the links on the page and gets the next possible page for you. This is not that good
Some download accelerators just use a better FTP program, but don't pay for that. Just tweak your connection and you should be able to get about 50K/s downloads. Sometimes mine hits like 98k/s and I'm on cable!!
Max