So if I buy a DCC controller it will be a lot easier for my layout?

I am planning to make my layout a complete copy of this basically just that every line of track is going to be connected unlike this one where the out side track is not.  http://www.youtube.com/watch?v=py1Il4hMWK8

So I this case I am planning to run 4 trains on the same track so I will definitely need to buy a DCC controller if I want them to be going at different speeds and in some cases completely stopped. Right?

Thanks

The controller I currently have a Power Pack and speed controller. http://www.hobbysetcohio.com/bac44212.html  However.. it does say it appropriate for DCC trains. I do not think I have a DCC train. This is the train I have right now... http://www.amazon.com/Bachmann-Trains-Ft-Unit-Santa/dp/B0006O4060

Can I run a DCC train with my current engine?

Thanks.

Hi guys. This question might sound a little dumb but I am new to this stuff. First, is there a difference from a DCC on board train and a DCC sound on board train? Second, if I get a DCC on board or a DCC sound on board train (if there is a difference), do I have to have a DCC on board or DCC sound on board controller? Right now I have just a very simple starter controller.

Thanks.