rtorrent and max_downloads_global

[cagnulein]

I'm using with success rtorrent on my raspberry from my very first day with this board.
Now I would like to tune it better in order to allow me to watch some movies while I'm downloading some torrents.
I saw when I'm downloading more than 1 file, rtorrent eats more than 30% of the cpu, so I would like to limit 1 download at time.
I found max_downloads_global and setting it to 1 seems is useless (continues downloading all the files in the queue).
Any ideas?

Thanks