I had Phoenix sound installed with a speaker fitted in both units and this combination makes a lot of noise as you can imagine. More recently Neil fitted a couple of replacement smoke units which were readily available through a number of US dealers.
Looking in at the USA Trains web site it would appear that the Calfs are no longer available although I could stand corrected if anyone knows differently?
Please check my youtube link should you be interested in seeing them run
http://www.youtube.com/watch?v=6p0wDH9Nqdw
With my interest moving more to live steam nowadays, should anyone wish to own these I am sure we could agree on a deal to favour both parties and I can be contacted directly through GSC.