RE: What is a good engine for a Tower Kaos?
What IS your skill level?
If you've soloed then a Kaos is within the abilities of anyone ready to move on from a trainer depending...... depending on their confidence level.
As you progress, each model that pushes your envelope is a risk. Every one of them. The risk is greater when you're less confident and less when you're more confident. The Kaos is not a trainer that returns to neutral if you pull back the throttle and let go the sticks. But it's nowhere close to being edgy or touchy. It's actually a very comfortable to fly model with out any bad habits.
Any model that you're worried might be too much for you probably is. Any that you think might not be too much is a good next plane.