Usually an FM transmitter, under 5 watts is used.
Your audio path is going to look like this:
Server -[AES/Cat5 Out]-> (Optional: D/A Converter) -> Cinema Audio Processor -[XLR Out]-> Mixer to down-mix from 5.1 to Stereo 2.0 (and allow a mic to be connected) -[XLR Out]-> Compressor (Audio will sound funny / audio will jump around from too quiet to too loud without it) -[XLR Out]-> Commercial FM Transmistter such as this: https://www.decadetransmitters.com/en/transmitters/fm-series
