With the Ramsey FMLP1 External FM Broadcast Low Pass Filter Kit you can clean up the output and properly match your power amplifier.
The FM Low Pass Filter kit came about while designing the PX1, Professional FM Broadcaster. The FCC Ruling 99-25 created a class of radio stations designed to serve localized communities by authorizing new classes of non-commercial low power FM radio services (LPFM). In order to meet the stringent guidelines of the FCC, the PX1 underwent months of design sessions and many hours of painstaking tests. One of the secrets to its clean output is the FMLP1.
If you own one of those spectrally dirty "import exciters" you'll definitely want to add the FMLP1 to the clean up the output and properly match your power amplifier. Maximum input power 50 watts.