Thank you everyone. This has been very helpful. I will go with four power districts. The forth being the future yard and turntable. I will have a lot of accessories with activator/uncouple tracks for the grand-kids and me to play with. May need a 5th power source for that. We all know O Gauge Lionel/MTH is not an inexpensive hobby to craft correctly with fun accessories. For the last seven years, every month, I had a direct $$$ deposit which went automatically into a train account. In addition I was picking up accessories as they became available. Let's just say I had an O Gauge 401K !!!!!!
Thank you Again. D