First of all, just a friendly note in case you didn't know: be careful about posting about stuff that might be illegal on these forums. The moderators want to keep everything clean. I'll go ahead and assume you only torrent files that are legal to do so, and are asking about them.
I've never used qTorrent before, and it sounds kind of obscure to me, so it's entirely possible that it is inferior and can't handle fast speeds. But if it works like it should, your download speeds should only be dependent on how many other people are offering that file to download, unless you have a bandwidth cap set or something. Why are you looking to replace uTorrent?