Karl, we are using AC track power since we are also running TMCC and Legacy engines on the layout. In S gauge, Older Legacy and most TMCC will not work on DC track power, hence the need for the in-engine rectifier for Blunami. 2A is generally adequate for the AM single motor diesels. My AM diesels draw a full 2A pulling a 15 car freight up a 2.2% grade.
S gauge Legacy engines will not work reliably at 12V to 14V. For full smoke volume and 100% reliable operation of the electrocouplers at least 15V at the engine pickup wheels is required.