aria2 is a lightweight multi-protocol & multi-source command-line download utility. It supports HTTP/HTTPS, FTP, BitTorrent and Metalink. aria2 can be manipulated via built-in JSON-RPC and XML-RPC interfaces.
Usage of aria2 could speedup download process massivly.
It's not necessary to start x instances of wget but only one aria2 instance and it's possible to use parallel connections for downloads