km has a lean and mean download assistant, but the problem that I have been having is with my ISP which DCs me every few minutes, so if I'm doing a large download, I have to start over again.
To solve this problem, I have found that by installing the download assistant FlashGet http://www.amazesoft.com/ and using the Opera plugin, np1gcf.dll, from the same site, which I installed in km plugin folder, Viola, I get a restartable download assistant. For those who have the luxury of broad, FlashGet will greatly speed up download speed because it opens up multiple pipes.
FlashGet is freeware, but be warned that it comes bundled with spyware, but fortunately, the spyware can easily be weeded out with a program like Lavasoft's AdAware.