Can you explain how? I have to say even 10 Mbps should be adequate for that, maybe 20 Mbps for 3 people maxing out at the same time. TWC offers 50 Mbps in my area, and they don't even support DOCSIS 3. What percentage of end users even have DS3 support available? I know older DOCSIS 2.0 modems were limited to 42 MBps, but even so ... Don't the "vast majority" have a limit on bandwidth?
Like mentioned by everyone else, any DOCSIS 3 modem will fit what you are looking for. You can find the Arris WBM760A Touchstone DOCSIS 3.0 Cable Modem on Amazon for $57, I personally use this modem. For the cost, it is really good. This device has also been approved by Comcast to be compatible with their extreme speed tier. A list of compatible devices can be found here: DOCSIS Devices