Hi Vincent, not sure what are you connecting Reach RS2 to, but if you want to have a good time sync you can connect to the PPS pin, which is synchronized to a full second with very high accuracy. Not available on a Mac or Windows machine, but if you are using something like a Raspberry Pi it could totally work.
A typical setup is to listen both to the PPS pin and to the NMEA stream. You read the absolute time from NMEA and get the precise synchronization using the PPS output. GPSD actually has support for both NMEA and PPS. A much cheaper setup than buying a dedicated NTP server.