If it is so, then go to Soulseek and go to it's Options (I'm not familiar at all with Soulseek so I have no idea where you wan find that). Find the port that it is using and then go to LW's Options, and input that port there (it's in Advanced). You may have already tried that, so sorry.
Also, getting fast speeds does not depend (IMO) on how many sources you a dld has as much as what connections the hosts have. While a file hosted by 100+ users will be more likely to finish, if you try to dld a file that is hosted by only 6 users who all have a T3 connection and you manage to connect to all of them, then you'll get crazy speeds. For instance, before I moved to a 2Mb connection, I could reach max speed with only Cable users. Now I can't (not that I'm complaining or anything). If I want to do that , I have to look for T1+ users.

__________________
iMac G4 OSX 10.3.9
RAM 256MB
LW 4.10.5 Basic
ADSL anything from 3 to 8Mbps/around 1024kbps

"Raise your can of Beer on high
And seal your fate forever
Our best years have passed us by
The Golden Age Of Leather"
-Blue Öyster Cult-