The amperage does not divide by number of motors, unless wired in series. If you wire in parallel, the amperage accumulates (ADDS) to a total.
On sound decoders, the horn is not a separate function. If you want to add some sort of horn device to a 408, you have to use one of the functions. The NCE D408SR is NOT a sound decoder. it has not built in sound chips or functions.
Sound decoders are a whole different animal and are not nearly as standardized as motor control. The NMRA standard defines the motor control CVs and how they work. To be NMRA compliant, a decoder has to follow these standards. Sound is/was not part of the standard, so each company has gone their own way and added variouis memory and access methods to create hundreds of control variables in some cases.
Most sound decoders with a horn installed, and many have a choice of 8 or more horns. Also, if want to download your own, I think you can. To download you have to have a programmer specific to the individual decoder brand as near as I can tell. QSI, SoundTraxx, Loksound are a few of the major sound decoder suppliers. MRC and Digitrax may have some also. I have not checked to see if NCE makes sound decoders or not.
I am not well versed in sound. I have installed quite a few sound decoders, but I just used the sounds available on the decoder and the options they offered. I have not downloaded new sounds. And to be honest, I can't tell the finer points of sound. I can tell an EMD from a Baldwin and and Alco, and I think I can hear a turbo but I am not that good at picked the sounds by hearing them.
