The average HD stream requires about 30-35 MBps. Even if you had a perfect signal and a 300N connection, thats still only about 38MBps. So that one stream would eat your whole pipe.........
Your marketing department needs to be
terminated and replaced based on your claims. I don't buy into the hype myself but there are many people that will see your HD claims and buy the inferior product.
See for yourself:
http://www.dlink.com/products/?pid=548
"The Duo technology in the DIR-855 supports dualband (2.4GHz & 5GHz) wireless signals at the same time. This allows you to check e-mail and browse the Internet using the 2.4GHz band while
simultaneously streaming High-Definition (HD) movies and other media on the 5GHz band. The DIR-855 is designed for users looking to get a
true HD wireless connection that can handle multiple HD video streams throughout the house,"...