I believe Bachmann sells a booster for the Dynamis, but I am not certain.
Your dynamis should power a good sized layout, provided you use a 14-12 gauge wire bus under the layout, and provided you keep the feeders to the rails short, say under 16". Also, you should place a pair of those feeders, 20-22 gauge, every 6-8' of track.
If your bus has to be longer than 30', or any feeders longer than 3', you will have some voltage loss that could affect your locos. Once you run 12 gauge wire longer than about 30', you get reductions approaching half a volt.