Broadway Limited Blueline and Paragon 2(dc/DCC) is for DC only and you will have to purchase their add on controller once to access all the sound You can also program the sound with it.
Atlas, Proto (Walthers), Intermountain and Broadway Limited all with QSI sound will work on DC only and Dcc You will also have to purchase their add on controller once to access all the sounds and program.
I have purchased several Blueline, Proto, Broadwayand Atlas Gold engines with factory sound for under $125.00 New on Ebay from dealers. The seperate controllers are around $50.00.
Bachmann has just come out with a sound value line of locomotives but they use soundtrax and need to run on DCC or you would have to purchase the MRC black Box (no programing) to get all the sounds. The MRC tech 6 ( has programimg)would also work for running DC and DCC sound units .
Athearn is now also using Soundtrax for sound.
With all the above you will get only the sound of the Engine or chuff without an add on controller to get the Bell/Whistle or horn. Except the Qsi system you can flip the reverse switch on your powerpack to use the bell or horn/whistle.
Any seperate DC sound decoder will run $45.00 to $100.00 and you will have to install them. The engines with factory installed sound are a better way to go for me.
Mrc also makes a model 1025 sound box and speaker for diesel and steam sound that is not in the engine and you can have sound for everything you are running just not in the engine.
Bob