You may find that your ISP is already offering tiered Internet service -- mine does (Comcast).
If that is the case, you better check and make sure you are getting the speeds you are promised. How might you do that? Try Speedtest.net. You will need Flash 8, though they promise a Flash 7 version for Linux users (this week).
Fortunately, I had pretty good results with the testing. I wonder if Comcast keeps up at the higher speeds.