I have a single fairly low-power PC in one location on wired 1Gbps ethernet running Plex capable of serving any content to any destination, inside the house or streamed over the internet, without hiccups. That's not to say I am the only person satisfied with their configuration, but to mention the possibility that you're having an issue unrelated to your specefic device/software combinations. There could be any number of variables from wiring faults to wireless interference, disk performance to data corruption. i.e. maybe the car runs fine, but you're driving on a bumpy road and no amount of changing tires and suspension is going to fully solve for the surface irregularities.
Can you tell us more?
Can you tell us more?