Now dont worry,everyone can use their fav Download mangers in FireFox.Simply use this tool to integrate ur fav download manager to FireFox.
It's aptly called "Download With".
*downloadwith.mozdev.org/
Download it here:-
*downloadwith.mozdev.org/installation.html
Once u got this extension,u can use any download manager to download all file 8)
Also,if u use Download Express,then u can download a plugin to work with FireFox.
Mozilla FireFox plug-in
Click here to download MetaProducts Integration plug-in for Mozilla FireFox browser.
To install the plug-in, please drag and drop the file to FireFox browser window using Windows Explorer. Then please restart FireFox. Now you can use the link right-click menu item "Download Express: download this file." Also, FireFox will offer you to use Download Express to download files.
Some other good FREE downloaders are:-
Download Express
*www.metaproducts.com/mp/mpProducts_Detail.asp?id=18
FreshDownload
*www.freshdevices.com/
StarDownloaderFree
*www.stardownloader.com/
LeechGet
*www.leechget.net/en/