Chad
O Scale 2 rail has never had a commercially made power supply that became a de facto standard like the ZW or Z-4000 have been in O scale 3 rail.
What you need will be defined by your power demands.
What locomotives do you have? Are they conventional DC or do they have sound decoders?
Do you plan to run passenger trains with incandescent lights? If so how many cars?
Once you define your amperage and voltage needs they you can decide on what power supply best meets them.
Bridgeworks makes very good DC power supplies.
Adding bridge rectifiers to a modern AC power supply like a Z-4000 is another good option. It is also inexpensive if you already have a new AC transformer.
If you have factory 2 rail MTH locomotives with Proto 2 you can run them on AC or DC power in addition to DCS. Proto 3 locomotives are very versatile, they will run on conventional AC, conventional DC, DCC or DCS.
