Johns not kidding about the welding. I guess the question is, do you really need the extra brick?
Are you popping the breaker on the one you have from overloading.
I initially had 2 bricks through a TPC unit because I thought I "needed" that much power for my 10'x16' layout. Any derailments resulted in spot weld marks on wheels and rail.
After John advising that it was " a ton of power", I disconnected one brick and discovered can run my trains just fine without it. At the same time no "welding" during a derailment, I don't think there are even sparks.
FWIW I typically run 2 scale steamers with either 6 lighted passenger cars or about 15 freight cars and have a scale switcher working in the yard with smoke units on.
I've yet to pop the breaker on my 1 brick.
Getting power to the layout is also very important. I run 14 ga buss with 14 ga feeders every 10'. No voltage drops of any kind.
We, (The Fort Pitt Hi-Railers Pittsburgh, PA), use the two brick set-up for the Turntable/Roundhouse module. When all the stub rails are filled, along with the (4) Roundhouse spurs, there is enough load on the circuit, that on initial start-up, the thermal cut out on (one) PH 180 will pop. Up and running, and then you fill the display with engines there is no problem, your only operating two or three at one time. We added the second PH 180, as shown above. We can power the module, loaded with engines, with no problem. Again "More Power Tim" 
There are 14 stub-rails, some rails are long enough to handle (2) engines locomotives. The in-rush current , (14 or more units), on the TPC, turn power on, (TR #1/Aux1/Boost), is enough to trip the fast acting cut-out on the PH 180.
Mike CT
