It's possible, yes. However, it's not just one easy step. Steam, browsers, bittorrent, etc. all have their own preference. You'll have to go into the preferences of each program that you may download from and change the folder to which files are saved. Mozilla, for example, has a designated folder under the general tab of the options menu. You can change that so anything you download from your browser goes there. Steam has it's own folder, etc. etc. So change each one, and you won't have to worry about filling your SSD with that stuff.