Do you intend to stay with both scales? If you are going to have both and you have O scale MTH PS3 engines that you wish to run with DCC, the 10 amp NCE system would be a good choice to run both scales. On the other hand, the NCE Powercab will work fine for a HO home layout as it can be extended with extra boosters. The only real limitation to the Powercab is the number of throttles allowed which is 5 I believe. That's not a problem if you run mostly by yourself. As far as power supplies, if not included, use the one recommended by the manufacturer. Atlas or Kato sectional track is ok; Bachmann not so much. If it is a permanent layout, flex track is a better option as it allows more freedom. In that arena, there are many brand choices that are dictated by your specific needs. I suggest hanging out/researching on some of the HO-centric forums like MRH.
Brendan