I still think the first step is to figure out what the current draw is on the engines. As I mentioned earlier, I have a pair of the Weaver RS11s which have a similar drive and have very low current decoders. I think they are the NCE DS13 decoder. They are wired in series and not problems with them at all. These I believer are a much earlier import than the VO1000.
Once you figure out the current draw, you can decide what options area available for decoders. As I mentioned, the magenta/purple casing on the decoder indicates Soundtraxx and it looks like a TSU1000 (Tsunami) to me. If the current draw with motors in series is down under an amp, which is possible, you could probably just use that decoder with some cleaned up wiring.
