Back when I still had PS2 installed in my steamers, my Williams N&W J 611 measured around 1.5-1.75 amps, all the others were under 1amp.
The RCS Australia system I use now is rated at 3 amps and should be plenty. Currently all I have hooked up inside the engine is the dc can motor, headlight, and back up light. I do have 1 steamer (RailKing 2-8-0) that has a MyLocoSound card installed along with the RCS system, but I'm not sure what the power draw is, only because I can't figure out how to measure it (the loco has to be moving so I'd have to mount the meter on the engine somehow to get a reading).
The J weighs 14.2 lbs with the lead weight installed and around 12 lbs without. I've pulled over a dozen passenger cars with it (approx 2lbs each) without any issues of it shutting down.
