Download managers will help, overtime, with any system that has flakey speeds and pauses, or shuts down intermittently... halting lost downloads.
They make a difference on Satellite connections, and phone line modem connections... but their main use is for reliability.
However no download software will speed up the internet connection you have.
On some systems they break up the download into a number of pieces that are downloaded at the same time... but still that ethernet or modem connection is what controls speed.