that will protect a docsis 3.0 modem, have at least 8 outlets and won't break the bank?
Best protection for that coax cable is a wire. Coax cable must drop down and connect short (ie 'less than 10 feet') to single point earth ground via a wire. Wire is superior to any protector. Then a surge does not enter the building on that coax cable.
Some wires cannot be connected directly to earth. That is what a 'whole house' protector does. Make the same connection to earth when a utility wire (ie AC mains) wire cannot connect directly.
Surges seek earth ground. Either you connect energy harmlessly to earth before it enters a building. Or that surge is inside hunting for earth destructively via appliances. Only you make that choice. Only you decide what path a surge uses to find earth. Once inside, nothing (as in nothing) will stop or absorb the typically destructive surge.
Informed consumers earth a coax cable, before it can enter the building, to have best protection. Much fewer and informed consumers earth one 'whole house' protector from more responsible companies such as General Electric, Siemens, ABB, Square D, Intermatic, or Leviton - to name only a few. A Cutler-Hammer solution sells in Lowes and Home Depot for less than $50.
Above is protection for all appliances. Some also need protection for the building. So lightning rods are earthed. In both solutions, neither a protector nor lightning rod does protection. Both solutions are only about where hundreds of thousands of joules dissipate. Both solutions are only made better by upgrading the only thing that does protection - earth ground.
Essential for any protector is the low impedance (ie 'less than 10 foot') connection to earth. A ground wire from the breaker box and from the coax cable that must have no sharp bends, not be inside metallic conduit, no splices, as short as possible, and must route separated from other non-grounding wires. Again, protection is never about a protector. Protection means energy is not hunting for earth destructively inside the building.
Only effective solutions will discuss where hundreds of thousands of joules dissipate. No previously recommended solution does that or even claims protection from destructive surges. Even one number says near zero protection. Only you choose how hundreds of thousands of joules connect to earth.
If a modem needs protection, then so does the furnace, air conditioner, every clock radio, the TV, chargers for mobile phones, dishwasher, etc. Informed consumers protect everything for about $1 per appliance using the only solution proven by over 100 years of science and experience. Earth one protector from more responsible companies. A superior solution - from over 100 years of well proven science - costs that much less money. Coax cable has even better protection only using a wire from a ground block to single point earth ground.
Above is only a secondary protection system. Each protection layer is only defined by what does the protection. You are strongly advised to also inspect your primary protection system. A picture demonstrates what to inspect:
http://www.tvtower.com/fpl.html
One fundamental fact exists. And will not be discussed by ineffective (profit center) solutions. Protection is always about where energy is absorbed. A protector is only as effective as its earth ground.