Merlin,
Your OP repeats a mistake we all make when starting out. Layout SIZE doesn't really matter when it comes to transformers. As long as you have enough leads running out to the track system, you'll be fine. What eats wattage is motors and light bulbs.
So for your CW-80's, you need to figure out how many motors and light bulbs you plan on powering with each transformer. The track itself doesn't "use" power any more than just a wire "uses" power. IF the track has automatic switches running off the track power, then you need to figure in the momentary power of the switch motor, plus the continuous power used by the indicator lights on the controller and the switch itself.
An engine uses power for the motor(s), the headlight(s), the sound system, and the smoke unit. Passenger cars can chew up all kinds of power... especially if they use incandescent bulbs. Cabeese as well.
Jon 
