Not the entire house, but the coax between the pole and modem, yes. That is a power supply for a amp. Amps can cause issues with speeds, specailly upload. How is the coax wired in your house? Why do you need a amp? Do you have a lot of TV boxes in the house? If not, I suggest running a coax from the street/pole directly to the modem and get rid of the amp.
BTW, I am not even sure how you are getting 1Gbps without OFDM or OFDMA. What does a speed test show? I doubt 2Gbps is available in your area without that signal. That is the whole purpose of DOCSIS 3.1. What model modem do you have?