Well it depends. If you're only running 2 finders (1 G3N and 1 G2N) you won't need the black box (5port Switch) but you will still need the 2 ethernet adapter cables (AS EC QDE) and a single ethernet cable to go between them. The MEGA 360 will connect through a transducer port but be shared across the network through the ethernet connection.
Now, if you have i-Pilot LINK on your trolling motor or a 3rd Gen 2 or Gen3 unit, then you will need the 5 port switch and adapters for each Helix plus and ethernet cable for each Helix to reach the switch.
Brian