I suspect the decoders will be like the factory installed
ones from Bachmann. They do not look like the ones you buy from DCC
suppliers that are fairly small shrink wrapped. The board is almost
as wide as the tender from what i have seen. I think there are two
different boards in the Spectrum's, a decoder board and maybe a light
board from what I see in the Spectrum PDFs.
I have one Roundhouse 4-4-0 that came with MRC sound and the decoder was almost as wide as the tender and wide open, no shrink tubing around it. It was replaced by a Micro.
Since SoundTraxx is already supplying Bachmann, it would not be
too big a deal to supply Athearn since the factory programming is the
biggest issue.
My Spectrum's were DCC ready, no decoders, only a lighting PC
board with NMRA socket.
Rich