This is going to come down to what you plan on running around your loop.
- If you just have a single engine or two with freight cars you're probably going to be ok
- If you have a few engines, smoke, and a bunch of lighted passenger cars then you might see some power fluctuations.
I had a similar loop set up in the past with the Santa Fe PW Celebration set and my CW-80 couldn't handle it. I ended up buying the GW180 set and it was fine.
Just so you know my Lionel 180 powerhouse still powers my Legacy setup today with 3 loops, multiple trains, tons of smoke, lights, etc...