DCC is still the only open source system available as far as I know. All the others are proprietary it seems. This means that DCC components from different mfg can work together - with some exceptions.
Also DCC decoders and systems have advanced a lot in 15 years.
So my advice is to research some of the systems.
And probably it would be worth looking into the major 3 rail systems such as MTH DCS and the current Lionel system. Note that you cannot get decoders for the MTH system without buying their locomotives as of the last information I have. In other words the only way to use DCS is to buy locomotives and controllers only from MTH. I don't know about Lionel but I think it is the same with theirs.