Part time hobbyist here. See also total newb!

Santa got my son an O gauge Lionel North Pole Central kit for Christmas when he was 3. He is nine now and since he gets a few cars and accessories each year from Santa his layout has gotten quite large. We are pulling something like 15 feet of cars on a 45 foot long fast-track layout (over carpet) and basically you have to take the transformer to 100% to even get it to move, it still slows noticeably in the corners. We are still using the transformer that came with it which I am not even sure if it is an 80w or a 30w the pics look the same to me. I think it is an 80w. Question is, can I add a second transformer ( I don't think I can) upgrade to a larger one, or add another engine, to help move the cars along. I believe the answer to be that I need to upgrade the transformer, I have tried to research what I should get but I am pretty baffled by the options. A ZW seems to be the logical move up, would it handle what my setup entails? The new ZW-L seems to be pretty much identical to the ZW to me is there a difference I am not seeing? And then there is command and control which would be nice I guess but it seems to be hard to justify plunking down that kind of money for a set that ONLY goes up at Christmas. That is also kind of my concern about a ZW-L, It seems to be three times the price of the ZW but does the same thing. Appreciate any help you might offer. Looking forward to spending a day here decorating the house and getting the train out and hope to have stuff in place so he can really play with it again. ~Jon