The 50S and the 5S already come with the HD speakers included so the SC-A0325 for the 50S is not necessary and the SC-A0326 for the 5S is not necessary.
Here are which Sena headsets are compatible with the HD speakers:
SC-A0325 - HD Speakers Type A
- 20S EVO
SC-A0326 - HD Speakers Type B
- 10C EVO
- 10C Pro
Note: To use the HD speakers on a compatible headset, the firmware version that includes HD Speaker Support needs to be installed on the headset.