No one has 5 mbps, except for Fiber Optics maybe, but only 1/4 of America can afford it and need it.
What are you talking about? I have 10mbps.
What's the highest download speed you've ever gotten with your isp? (just *8 of that and that will roughly be your thing.)
Remember that it's MEGA BITS... not megabytes.
EDIT: like if you get over 640kb/s on downloads you will be able to use HD.