I'm confused...are you using BearShare or LimeWire (cos you've posted in both sections)? Can you let me know please?

Modem is the slowest speed, then cable/dsl, T1 & T3 is the fastest.
The higher the bitrate, the better the quality & also the bigger the file. Don't bother with anything lower than 128...sometimes that's crappy too so I go for at least a 192 bitrate.

Files that sit connecting for ages & then need more sources are usually fakes. There's more info & tips here
Fake files showing up in search results