There is so much more to "speed" then a stable line. Yes, the signal levels to your modem are important, and so is number of people on your node. But usually your ISP makes up only 1/3rd to 1/5th the bulk of the network your going over to reach your destination. Theres the backbones and fiber that cross the country, different media server farms, routing logs on routers, over burden servers, and so on. Do a traceroute sometime and google some of the names that come up. You would be shocked how much of the internet is maintained and dependent on companies you have probably never heard of.