Rivarossi FEF 4-8-4 and Genesis Challenger Decoder Questions

I want to run two HO engines together for a steam doubleheader but my Rivarossi FEF 4-8-4 is DCC ready with no decoder installed,does anyone make a proper sounding decoder that will fit my 4-8-4? I also want to change the decoder in the Challenger to correct the sound for this engine can someone please advise? Thank You, Tony.

Soundtraxx Tsunami

Genesis Challenger: I plan on using a Soundtrax Tsunami as replacement sount in the near future.

Rivarossi FEF: If the DCC plug in located under one of the boiler domes, you may need to rig a plug extension back to the tender in order to install a sound decoder in the tender. I would use Soundtrax Tsunami for sound.

If sound is not an option, Digitrax makes an N-scale decoder which is small enough to fit in the space under the dome. You may want to drill some small vent holes in the dome to protect the decoder from over-heating.