I do support for IPTV for work.. for SDTV you need roughly 3-4 mbps, for HDTV 6-7 mpbs. The lower end of those estimates is fine, but it's good to have a little extra. Make sure you factor in other traffic for example.
If you're ONLY going to be using 1 computer at a time and watching HD Netflix 6 should suffice. If two people are or other people are using the internet at the same time.. or you're going to be downloading .. then add bandwidth as needed.