Are you planning to run your DCC equipped locomotives during the change over period? If so you'll need to continue using the Lenz system to provide power and run them; RailPro won't be able to control the DCC loco's and the DCC equipped loco's won't run on DC power.
For a DC power supply, firstly I'd recommend the PWR-56 as an easy way to get started, it's designed for the purpose and the cost isn't so astronomical if it's gotten as part of the starter kit, but I do realise that many want/need something beefier or cheaper. Some of us are using/have switch mode power supplies like these:
There are heap of these type of supplies on places like eBay, though not all are created equal and price varies a lot too. You also have to wire the mains power to them yourself so the mandatory caution about don't unless you know what you are doing applies.
Without knowing any specific's like how large is the layout and how many loco's you run at once a good guess would be a 5 Amp power supply should suffice for most scenarios. RailPro has a nominal voltage of 14 volts but you won't commonly find that voltage so you'll have to choose lower like 12v or 13.8v, or
IF the power supply has a voltage adjustment you can go higher (15v) and use the voltage adjust to lower it.
If your layout is very very small, like a simple oval of track on a 4 x 8 you could possibly get by with a wall-wart type of supply, you can get these up to as couple of Amps capability but for anything bigger don't try that path.
The power supply needs to be a regulated supply. That means as the load increases (more locomotives running) the voltage doesn't drop off. Most quality supplies would be regulated but you'll always want to check.
Apart from that I can't give a you a whole lot more info I'm afraid.
- Tim
