Thanks for all the input everyone!! IT's a HUGE help!
The only reason I was wondering was because I'm actually using plans from the Atlas-O 3-Rail Layouts Book. It has 2 Atlas 80 Watt Transformers for the whole setup. Obviously that doesn't include accessories, but I'm sure it'w meant to run at least 2-3 trains at one time. According to this setup, I'll have 20 more watts than needed.. Plus I do have a Z-500 which I believe is 54 Watts. I was planning on using that for all the lit accessories.
I got a DCS/TIU setup.. I have the PH-180 hooked to the FIXED Voltage IN. The FIXED Voltage OUT goes to a 12-port terminal block, which goes to the power drops.