Yesterday while I was googling, I found a torrent-client called Transmission. It's a freeware and very light, very simple with its interface, and also it's very easy to configure maximum download or upload rates, at least it doesn't make me so confused anymore. It works on my Mac OS Tiger 10.4.9.
Read more : here and screenshot
Download : Tiger version or other available OS
P.S : I'll capture its freeware on my desktop later .. *Peace*