Previously stated by some user to 'search for more sources (files) of the file you're downloading while you're downloading it, to increase speed'.
This is correct, but have you noticed that even though there are hundreds of sources, you're only downloading from about 2? Well, what am about to say might not be the reason, but it has helped me.
When you start the search while downloading, the Auto-search will be searching on and on, getting more and more users. Stop it when it reaches around 50 sources (or a reasonable value depending on the files inconceivability), but make sure you stop the search. This is the most important part.
Then, use a program like 'Speedup' to do the 'find more sources' job. Set it to '20' seconds between cycles.
After a few minutes, you would notice your download getting more and more sources, as it did for me.