[BrookTrout]

You want DSL offered by your phone company, rather than Cable - which is a shared bandwidth (like you said, the more people in your general area who are using it, the slower it will be). DSL speed remains constant regardless of if your neighbors have it/are using it.

Also, your roommates' laptops probably play no small part in you being unable to connect to Live... again solved by getting your own connection.