For this photo of a dozen engines with smoke units OFF, the Z4000 powering the turntable indicated 9.9 amps and couldn't hold that current for very long. Some of the whisker tracks had to be turned off between shots.
The O.P. should first isolate the engine storage sidings so they can be powered off.
10 amps is sufficient to run two or three trains on a loop. Each loop should be isolated from the other (if they are connected) with fiber pins in any crossover tracks. Each loop should be powered with a separate power brick.
Don't switch to a TPC. The breaker is less sensitive than the internal breaker in the 180 Powerhouse bricks. As GRJ mentioned, those of us who have tried the high amperage the TPC 400 is capable of are wary of the heat and damage caused by any derailment/short.
A 12x20 layout should not need multiple power districts on the same loop - just power each loop separately. If you have a big yard then that could be its own power district with its own power supply.
