Under the "New Users Start Here / Introduce Yourself" thread, Jeff asked, "Any input on how to go about installing the system, i.e number of power modules needed, where to locate said modules ( grouped in one place or distributed about the layout) etc. and any other tidbits will be greatly appreciated."
As they say, "it depends...."
Ring advertises that the PWR-56 has 56 Watts of output power to drive 15 or more typical modern HO scale locomotives.
I have three on my layout. My layout is an around the room, double-deck arrangement with a center peninsula. The room is ~21' x 20'. I have a construction blog about it over on the MRH website (I think you know that). Just search on "SP Lordsburg Sub - Construction".
* One for both the upper and lower return/staging loops - each has seven (-7-) tracks.
* One for the lower operating level.
* One for the helix and the upper operating level.
Based on the way I have them allocated, I'm thinking I won't ever approach having 15 locos on any one of them simultaneously.
Mine are all located in one central location in the center peninsula, so its not a long reach to any part of my layout.
Hope that gives you an idea of what you might need for yours!