sign up for gigabit download speeds
actually that won't guarantee anything, what determines down speed is the upload speeds of the hosts.
most of the settings are for telling ktorrent how many concurrent downloads you want and and how many connections to each torrent you want. make sure you have enough.
after that it depends on how many seeders are offering the torrent and their uplod speeds
if you have a torrent with one seeder then you are at his mercy if he is online or not
there are settings in ktorrent to slow down transfers so you dont take up all your bandwidth, but those are off by default.