Although I have seen and heard some fantastic Model RR sound systems that are installed in locomotives, coal tenders, and trailing boxcars...they seem too tinnish and low fidelity for my likings.
I went to a train show and they had full size speakers blaring from under the table, and the scene seemed so real at 80db.
The MRC Soundstation 312, and the MRC SyncroSound unit, if amplified using 2 microphones, hooked up to your home stereo provides very high quality sound effects. As too, a RR DVD, CD, video or cassette tape.
I still use HO hook horn couplers and analog DC...lol