Download managers are a great way to grab the files you need at the maximum possible speed. Until you decide you'd like to use your browser, of course, and find it's crawling along because there are only scraps of bandwidth left.
Install NetBalancer, though, and you'll be prepared for these situations. The program lets you assign download and upload priorities to your web applications, so you could, say, set your download manager to "low priority" for a while, and your browser would automatically get a better share of available bandwidth. Or, in emergencies, you can prevent an application from accessing the internet at all.
The program doubles as a useful bandwidth monitor, too, listing all your running processes, graphing current network activity, and detailing exactly which network connections an internet program has open at the moment. And so you could also use NetBalancer to identify malware, perhaps, by spotting its efforts to phone home.
There is an unregistered 'free' version of NetBalancer, you're limited to controlling the bandwidth of no more than 3 applications. We think this should be sufficient for most people, as you really only need apply it apps that will consume all your bandwidth, like download managers or P2P software. But if you need more, then you can upload to the unlimited NetBalancer Pro version for $29.95.
Recent changes include a digital signature, compatibility with Windows 8.1, and a few improvements under the hood, the most important of which is "Sync Edit": now you can edit the Sync settings remotely from your web control panel, for multiple computers at once.